Request Smuggling

Response poisoning in Apache APISIX 2.12.0 through 3.17.0 enables remote attackers to manipulate the gateway's serverless plugin routes so that victims receive attacker-chosen content or other authenticated users' API responses. The root cause is inconsistent HTTP request boundary interpretation - the defining characteristic of HTTP Request/Response Smuggling - applied within APISIX's serverless plugin execution pipeline. No public exploit has been identified at time of analysis, and vendor-released patch version 3.18.0 is available.

HTTP request smuggling in the Perl CPAN module Reverse::Proxy (versions before 0.04) allows unauthenticated remote attackers to inject arbitrary HTTP requests to upstream servers by embedding CRLF sequences in percent-encoded URL paths. The PSGI specification requires servers to percent-decode PATH_INFO before handing it to the application, meaning %0d%0a has already become a literal carriage return and line feed by the time the proxy appends it to the upstream request line - terminating that line early and promoting everything that follows to a second, attacker-controlled request. The injected request is attributed to the proxy by the upstream and can reach internal paths the proxy's own routing never exposes; on pooled keep-alive connections it may be delivered in the context of another client's session. No public exploit code and no CISA KEV listing exist at time of analysis.

HTTP request smuggling and header injection in libevent's http.c allow remote unauthenticated attackers to desynchronize an upstream proxy from libevent's own parsing, bypassing access controls. Affected are all versions prior to 2.1.13-stable and 2.2.2-alpha, where evhttp_header_is_valid_value accepted obsolete CRLF line folding in header values and evhttp_decode_uri_internal decoded %00 into literal NUL bytes that truncate paths in downstream C string operations. No public exploit identified at time of analysis; the CRLF weakness is patched in 2.1.13/2.2.2-alpha, but the URI NUL-truncation condition is not clearly remediated by the reviewed patches.

HTTP chunked trailer smuggling in libevent before 2.1.13 and 2.2.2-alpha allows unauthenticated remote attackers to inject security-sensitive header fields - such as Authorization or X-Forwarded-For - via chunked transfer encoding trailers that libevent merges directly into its request header store. In deployments fronted by a reverse proxy, the proxy evaluates the original headers while libevent processes the attacker-supplied trailers as authoritative input headers, enabling authorization bypass, proxy-header spoofing, and cache poisoning. No public exploit has been identified at time of analysis; vendor-released patches exist in both stable and alpha release branches.

HTTP request smuggling in the libevent evhttp server (http.c) affects all versions prior to 2.1.13 and the 2.2.x-alpha line prior to 2.2.2-alpha, letting an unauthenticated remote attacker desynchronize request boundaries when libevent sits behind a differently-framing proxy. Because evhttp mishandles duplicate and comma-listed Transfer-Encoding headers and accepts bare-LF chunk terminators, a smuggled second request can bypass proxy-enforced access controls or poison shared caches. No public exploit identified at time of analysis, and this is not listed in CISA KEV; a vendor patch is available.

HTTP request smuggling in Cesanta Mongoose embedded web server/network library before 7.22 lets a remote unauthenticated attacker desynchronize an HTTP/1.0 reverse-proxy front-end from the Mongoose back-end. A buggy length check in http_cb() (src/http.c) never sets is_http_1_0, so Mongoose honors Transfer-Encoding: chunked framing that an HTTP/1.0 proxy ignores, allowing the attacker to smuggle requests past the proxy and reach unauthorized functionality or alter application state. Rated CVSS 9.1; a vendor patch exists (7.22), but no public exploit and no EPSS/KEV data were provided at time of analysis.

HTTP request smuggling (CL.TE desynchronization) in Cesanta Mongoose embedded web server before 7.22 lets a remote unauthenticated attacker craft a request bearing both Content-Length and Transfer-Encoding: chunked headers. Because mg_http_parse()/http_cb() accept both and prioritize chunked encoding while a front-end reverse proxy that prefers Content-Length draws a different request boundary, an attacker can smuggle a second request that reads or modifies resources belonging to another user's context. No public exploit is identified at time of analysis; the issue is fixed in 7.22 which rejects requests containing both headers.

HTTP request smuggling in actix-http (versions up to and including 3.12.0) allows unauthenticated remote attackers to desynchronize backend request parsing when the service operates behind an HTTP/1.1 intermediary. The parser accepted requests carrying both Content-Length and Transfer-Encoding: chunked headers (the CL.TE variant) and silently selected chunked decoding instead of rejecting the ambiguous framing as required by RFC 7230, enabling an attacker to prepend malicious content to subsequent backend requests. No public exploit code has been identified and this vulnerability is not listed in the CISA KEV catalog at time of analysis.

Header injection in http4s blaze-server allows remote unauthenticated attackers to smuggle arbitrary HTTP headers - including X-Forwarded-For, X-Real-IP, and internal authorization headers - by embedding them in HTTP/1.1 chunked transfer encoding trailer fields, which blaze-server incorrectly merges into Request.headers. Applications deployed behind a proxy that sanitizes request headers but forwards chunked bodies with trailers intact are fully exposed: attackers can spoof client IPs to bypass allow-lists, forge HTTPS scheme indicators, inject internal authentication tokens, or force termination of pooled backend connections via a promoted Connection:close trailer. No public exploit code has been identified at time of analysis, and this vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Request smuggling in Apple ServiceTalk's HTTP/1.x implementation exposes services to request pipeline injection by exploiting improper parsing of malformed Transfer-Encoding headers. All ServiceTalk deployments running versions prior to 0.42.65 are vulnerable, with the CVSS vector confirming unauthenticated network exploitation with high integrity impact. No public exploit code and no CISA KEV listing have been identified at time of analysis, though the EPSS score of 0.14% reflects low but non-zero current exploitation probability.

HTTP request smuggling in System.Net.HttpListener across .NET 8.0, 9.0, and 10.0 enables unauthenticated remote attackers to bypass security features on Linux and macOS deployments. The flaw stems from inconsistent HTTP request interpretation (CWE-444), allowing crafted requests to circumvent authentication or access controls with high confidentiality impact. Exploitation carries high attack complexity (AC:H), no public exploit has been identified at time of analysis, and the vulnerability is not listed in CISA KEV, placing this in a monitored-but-not-emergency posture for most organizations.

HTTP request smuggling in Undertow's ChunkReader component enables unauthenticated remote attackers to inject out-of-sync requests, bypassing upstream security controls such as authentication layers or reverse-proxy ACLs. Affected deployments include JBoss EAP 7, WildFly, Red Hat Enterprise Linux 8/9/10, Red Hat Data Grid 8, Red Hat Fuse 7, Red Hat Single Sign-On 7, and several Apache Camel-based Red Hat products. No confirmed active exploitation or public proof-of-concept has been identified at time of analysis; the CVSS 5.3 Medium score reflects limited direct impact, though real-world risk in proxy-fronted architectures is meaningfully higher than the score alone suggests.

Cache poisoning in CoreBunch/Instatic through version 0.0.14 allows unauthenticated remote attackers to corrupt the shared process-wide render cache by supplying a crafted originating-page URL via the `u` query parameter of the server island endpoint `GET /_instatic/hole/<nodeId>`. Because the cache is keyed solely on `nodeId` without incorporating the `u` value, a single poisoning request causes every subsequent visitor requesting that node to receive attacker-controlled fragment content. No public exploit code has been identified and no CISA KEV listing exists; the product's early-stage, niche deployment footprint limits real-world blast radius, but the unauthenticated network vector and low attack complexity make exploitation straightforward against exposed instances.

Request smuggling primitive in h2 (pip/h2) versions 4.4.0 and below enables network-accessible attackers to craft HTTP/2 header blocks containing duplicate Host headers that the library forwards verbatim to consuming applications. When a consumer downgrades the HTTP/2 request to HTTP/1.1 - a common pattern in reverse proxy and gateway architectures - the resulting HTTP/1.1 request carries two Host header lines, violating RFC 7230 and creating an ambiguity that downstream servers may interpret differently, enabling cache poisoning, security control bypass, or session hijacking. No active exploitation confirmed (not in CISA KEV); no public exploit code identified at time of analysis; fix is available in v4.4.1.

Cross-user HTTP response poisoning in Traefik's default reverse proxy allows an unauthenticated remote attacker using HTTP/2 or HTTP/3 to smuggle responses into other clients' backend connections, potentially delivering authenticated or private content from one user to another. All supported Traefik branches through v2.11.52, v3.6.23, and v3.7.8 are affected in default configuration when fronting Go net/http or gunicorn/Flask backends, which are confirmed 'armed' (respond to CONNECT with keep-alive non-2xx without draining the body). A proof-of-concept is publicly available demonstrating reliable cross-user poisoning including a cascade scenario where 8 of 8 sequential victims read responses that were not their own; no CISA KEV listing was present at time of analysis.

HTTP request smuggling in Progress MarkLogic Server's HTTP App Server (versions before 11.3.6 and 12.0.3) lets a remote attacker desynchronize request parsing between a fronting reverse proxy and MarkLogic, enabling authentication/authorization bypass, session hijacking, and credential capture. The flaw is exploitable over the network without authentication (PR:N) and carries a critical 9.1 CVSS with high confidentiality and integrity impact. There is no public exploit identified at time of analysis and it is not listed in CISA KEV; no EPSS score was supplied.

HTTP request smuggling in aiohttp's server-side parser allows unauthenticated remote attackers to inject and misdirect HTTP traffic by exploiting a protocol-switch race in the WebSocket upgrade path. Versions 3.14.1 and earlier prematurely mark the connection as upgraded before the full request body is consumed, causing trailing bytes - potentially an attacker-controlled HTTP request - to be interpreted as WebSocket or pipelined data by the server or any upstream proxy. No public exploit code exists and the vulnerability is not listed in CISA KEV, but CVSS 4.0 AC:H reflects the edge-case nature of the trigger condition.

HTTP request smuggling in cPanel and WP Squared (by WebPros) enables leakage of credentials from other users sharing the same hosting infrastructure. The CVSS 4.0 vector confirms network-reachable exploitation with no authentication required but with passive user interaction and attack-specific prerequisites; critically, the subsequent-system impact is rated High for both confidentiality and integrity (SC:H/SI:H), indicating that successful exploitation crosses trust boundaries to affect other users or backend components beyond the attacker's own session. No public exploit code has been identified at time of analysis and this CVE is not listed in the CISA KEV catalog, but the scope-change impact makes it a meaningful risk in shared hosting environments where cPanel serves multiple tenants.

Response body/Content-Length desynchronization in undici's retry interceptor allows a malicious or faulty upstream server to induce HTTP response smuggling against downstream clients of proxy and gateway applications. Affected versions span undici before 6.28.0, the 7.x line before 7.29.0, and the 8.x line before 8.9.0. An upstream that deliberately returns a partial response with mismatched framing and closes the socket early can cause the retry interceptor to assemble a body of a different length than the attached Content-Length, leading downstream consumers to experience response desynchronization, connection hangs, or data corruption. No public exploit has been identified at time of analysis, and this is not listed in CISA KEV.

HTTP request smuggling exposure in Node.js 26.x arises because the HTTP server failed to reject incoming requests that exceed the configured maximum header count, creating an inconsistent parsing boundary exploitable by adversaries. Rated Low severity (CVSS 3.7) by the Node.js security team and fixed in v26.5.1 released 2026-07-29, the flaw is classified under CWE-444 and is most dangerous in reverse-proxy deployments where header-count enforcement differs between the frontend proxy and the Node.js backend. No public exploit code and no CISA KEV listing have been identified at time of analysis.

Request smuggling and policy bypass in Apache Traffic Server (branches 8.0.0-8.1.9, 9.0.0-9.2.14, and 10.0.0-10.1.3) arises because the proxy silently truncates over-long HTTP header names, causing two distinct header names to alias to the same value. A network attacker can exploit this desynchronization to smuggle requests past the proxy and bypass security or routing policy. No public exploit has been identified at time of analysis, but the CVSS 9.3 rating and CWE-444 classification mark this as a high-priority proxy integrity flaw affecting a core CDN/caching component.

HTTP/2-to-HTTP/1 protocol conversion in Apache Traffic Server 10.0.0-10.1.3 forwards origin HTTP/2 trailers to downstream HTTP/1 clients without the required chunked transfer encoding framing, enabling HTTP response smuggling. The CVSS 8.3 Scope:Changed rating reflects that exploitation impacts downstream HTTP/1 clients architecturally separate from ATS itself, with potential for cache poisoning, response injection, and limited information disclosure. No public exploit code has been identified and this CVE is not listed in CISA KEV at time of analysis.

HTTP request smuggling in Apache Traffic Server (versions 8.0.0-8.1.9, 9.0.0-9.2.14, and 10.0.0-10.1.3) lets remote attackers desynchronize proxy/backend request parsing because the server fails to reject the Transfer-Encoding header on inbound HTTP/2 requests. When ATS downgrades those HTTP/2 requests to HTTP/1.1 for origin servers, the improper Transfer-Encoding directive creates a parsing discrepancy that enables downgrade request smuggling. No public exploit identified at time of analysis and it is not listed in CISA KEV, but this is a well-understood smuggling primitive tagged by the reporter for information disclosure.

Request smuggling in Apache Traffic Server (versions 8.0.0-8.1.9, 9.0.0-9.2.14, and 10.0.0-10.1.3) allows remote attackers to desynchronize the proxy from backend origin servers by sending malformed chunked-transfer-encoded messages, per Apache advisory and NVD. Successful exploitation lets an attacker poison caches, bypass access controls, or disclose another client's information as tagged by the reporting source. No public exploit identified at time of analysis and the flaw is not in CISA KEV.

HTTP request smuggling in Apache Traffic Server allows unauthenticated remote attackers to interfere with how the proxy and backend servers interpret HTTP request boundaries, enabling cache poisoning and limited information disclosure. Versions 9.0.0 through 9.2.14 and 10.0.0 through 10.1.3 are confirmed affected per Apache advisory. The Scope Changed (S:C) CVSS metric reflects that exploitation crosses the proxy boundary to impact downstream backend systems. No public exploit code or CISA KEV listing has been identified at time of analysis.

HTTP response smuggling in IBM WebSphere Application Server 9.0, 8.5, and Liberty versions 17.0.0.3 through 26.0.0.7 allows unauthenticated remote attackers to poison intermediate caching proxies by exploiting improper handling of non-standard HTTP version tokens. Successful exploitation leads to high confidentiality and integrity impact through cache poisoning, potentially enabling information disclosure and malicious content injection into proxied responses. A vendor patch is available, though no public exploit code or active exploitation has been reported at this time.

HTTP request smuggling in IBM WebSphere Application Server 8.5, 9.0, and Liberty 17.0.0.3 through 26.0.0.7 allows remote attackers to poison request queues, potentially leading to unauthorized information disclosure and cache poisoning. The flaw stems from improper handling of TRACE requests, with a CVSS base score of 8.7 but no evidence of active exploitation or public exploit code at the time of analysis.

HTTP request smuggling in IBM WebSphere Application Server (versions 8.5 and 9.0) and WebSphere Application Server Liberty (17.0.0.3 through 26.0.0.7) enables remote unauthenticated attackers to poison shared HTTP connections between a front-end proxy and the application server backend. The CVSS 8.1 score reflects full confidentiality, integrity, and availability impact (C:H/I:H/A:H) but is constrained by high attack complexity (AC:H), requiring a specific proxy-to-WAS pipeline configuration to exploit. No public exploit is identified at time of analysis; EPSS is very low at 0.21% (11th percentile) and SSVC confirms no known exploitation, though technical impact is rated total.

HTTP request smuggling vulnerability in Rouille's proxy implementation allows remote attackers to desynchronize HTTP message boundaries using a CL.TE attack. Affected versions 0.3.3 through 3.6.2. Publicly available exploit code exists, but no active exploitation has been reported.

HTTP request smuggling in tiny-http versions through 0.12.0 allows remote attackers to desynchronize request processing between a front-end proxy and the vulnerable backend. By sending a Transfer-Encoding header with an arbitrary value, the library unconditionally switches to chunked decoding and discards the Content-Length, enabling request smuggling and connection exhaustion. Public exploit code exists, but active exploitation remains unconfirmed.

HTTP request smuggling in Rouille 0.3.3 through 3.6.2 allows remote attackers to bypass access controls by injecting bare line feed characters (0x0A) into header values. The framework forwards these headers verbatim to backends like Go net/http or Python http.server, which interpret the raw LF as a request delimiter, enabling a smuggled request with attacker-chosen method, path, and headers. Publicly available exploit code exists, increasing the risk for deployments using Rouille as a proxy.

HTTP request smuggling in libsoup (GNOME's HTTP client/server library) enables network-accessible attackers to inject hidden requests into backend streams by exploiting a parsing differential between libsoup's permissive chunked transfer encoding parser and strict RFC 9112-compliant frontend proxies. All libsoup versions are affected as tracked under CPE cpe:2.3:a:gnome:libsoup, with confirmed vendor impact across Red Hat Enterprise Linux 6.0 through 10.0. No public exploit code or active exploitation has been identified at time of analysis; SSVC classifies exploitation as none with non-automatable, partial technical impact.

HTTP request smuggling in SwiftNIO HTTP/2 allows unauthenticated remote attackers to inject headers or split responses via crafted HTTP/2 HEADERS frames that pass control characters through the HTTP/2-to-HTTP/1.1 codec. The vulnerability, caused by missing CR/LF/NUL/SP validation in regular header values and pseudo-headers, can be exploited when outbound validation is disabled or headers are forwarded without rechecking. Fixed in version 1.45.0; no public exploit identified at time of analysis and EPSS score is 0.14% (low).

HTTP/2-to-HTTP/1.x protocol translation in Netty's `netty-codec-http2` enables request routing bypass and HTTP request smuggling via duplicate `Host` header injection. When a client sends a HEADERS frame containing both the `:authority` pseudo-header and a literal `host` header, `Http2StreamFrameToHttpObjectCodec` and `InboundHttp2ToHttpAdapter` independently translate each into `Host` headers, producing an `HttpRequest` with two attacker-controlled, differing values. Downstream HTTP/1.1 components that prioritize the second header can be manipulated into routing requests to unintended targets. No public exploit has been identified and this CVE is not in the CISA KEV catalog, but patches are vendor-released for both affected release trains.

WebSocket protocol upgrade in Netty's V07/V08 handshakers completes without enforcing RFC 6455-mandatory `Connection: Upgrade` and `Upgrade: websocket` headers, enabling an attacker to silently switch protocols in a way that upstream reverse proxies and load balancers do not recognize as an Upgrade request. This desynchronization between proxy and backend creates a classic HTTP request smuggling vector (CWE-444) that can be exploited to poison shared connections, bypass proxy-enforced access controls, or hijack other users' HTTP sessions. Affected versions are `io.netty:netty-codec-http` prior to 4.1.136.Final and 4.2.0.Final through 4.2.15.Final; no public exploit code or CISA KEV listing has been identified at time of analysis.

Response-queue poisoning in the elixir-mint Mint HTTP/1.1 client library (versions 0.1.0 through before 1.9.3) allows a malicious or attacker-influenced HTTP/1 origin server to desynchronize a strict RFC-compliant intermediary from the Mint client on shared keep-alive pooled connections. The root cause is `Mint.HTTP1.decode_body/5` using Elixir's `Integer.parse/2` for chunked transfer-encoding chunk-size parsing, which accepts RFC-forbidden leading `+` or `-` sign prefixes, causing both parties to disagree on where one HTTP response ends and the next begins. No public exploit has been identified at time of analysis, but a vendor-released patch is available in Mint 1.9.3.

HTTP request smuggling in Eclipse Grizzly before 5.0.2 stems from the framework's inability to correctly parse malformed trailer header lines in chunked HTTP requests, enabling CWE-444 boundary-confusion attacks. Remote unauthenticated attackers who can send crafted chunked requests through a front-end proxy to a GlassFish-backed server can cause the proxy and Grizzly to disagree on request boundaries, smuggling attacker-controlled content as the prefix of a subsequent legitimate user's request. No public exploit code and no CISA KEV listing have been identified at time of analysis, though the CVSS 4.0 AT:P condition signals that specific deployment prerequisites must be met.

Request-response desynchronization in SAP Approuter lets an unauthenticated remote attacker send a specially crafted HTTP request that smuggles a second request past the front end, allowing exposure of other users' HTTP responses and denial of service against the application. The flaw carries a CVSS 9.1 (high confidentiality and availability impact) and was reported by SAP; there is no public exploit identified at time of analysis and it is not listed in CISA KEV.

Authorization bypass in Zalando Skipper (Go HTTP router/proxy) versions <= v0.26.8 allows unauthenticated remote attackers to defeat body-content OPA policies enforced by the opaAuthorizeRequestWithBody filter by sending the payload with Transfer-Encoding: chunked (HTTP/1.1) or as HTTP/2 without a content-length pseudo-header. Because Go's net/http sets req.ContentLength = -1 for such requests, Skipper's body extractor hands OPA an empty parsed_body, so a deny-when-forbidden-field-present Rego rule fails open (default allow) while the full attacker payload is still forwarded upstream. Publicly available exploit code exists (a passing E2E PoC test) and a vendor patch is available in v0.26.10; there is no public evidence of active exploitation (not in CISA KEV).

HTTP request smuggling in OpenVPN Access Server 2.7.2 through 3.1.0 enables remote unauthenticated attackers to inject or manipulate backend requests when the Access Server is deployed behind a reverse proxy. The server incorrectly accepts bare line-feed (LF-only, without carriage return) characters inside HTTP header values, creating a parsing discrepancy between the front-end proxy and the Access Server backend - the hallmark of CWE-444. No public exploit has been identified at time of analysis, and the vulnerability is not listed in the CISA KEV catalog; however, the CVSS 4.0 score of 6.9 with integrity impact on both the vulnerable and subsequent systems indicates meaningful risk in typical enterprise VPN gateway deployments fronted by load balancers or reverse proxies.

HTTP request smuggling in Ruby's WEBrick HTTP server through v1.9.2 allows remote attackers to desynchronize front-end/back-end request parsing by exploiting how WEBrick reparses a Content-Length value supplied in chunked trailers back into the canonical request state. Any deployment fronting WEBrick with a proxy, load balancer, or CDN that disagrees on message length can have requests smuggled past it, enabling request routing manipulation and information disclosure. Publicly available exploit code exists (SSVC exploitation status: poc), though EPSS remains low at 0.16% and it is not on CISA KEV.

HTTP request smuggling in IBM WebSphere Application Server (traditional 8.5 and 9.0) and WebSphere Liberty (17.0.0.3 through 26.0.0.6) lets remote attackers desynchronize how front-end proxies and the WebSphere back-end parse HTTP request boundaries, enabling request-queue poisoning, security-control bypass, and disclosure of other users' data (tagged Information Disclosure). The CVSS 9.8 vector rates all impacts high, but SSVC records no observed exploitation and EPSS is low (0.34%); no public exploit is identified at time of analysis, and a vendor patch is available. Realistic exploitation depends on WebSphere sitting behind an intermediary that disagrees with it on request framing.

Arbitrary file read in IBM WebSphere Application Server Liberty (17.0.0.3 through 26.0.0.6) lets remote attackers retrieve files from the server host when the restConnector-2.0 administrative REST feature is enabled. The flaw is classed as HTTP request smuggling (CWE-444), meaning inconsistent request parsing lets an attacker coax the server into exposing file contents it should not serve. No public exploit identified at time of analysis, and CISA SSVC records exploitation status as none; EPSS is low at 0.50% (39th percentile).

WAF managed-rule body inspection on AWS Application Load Balancer (ALB) can be bypassed by remote actors who fragment an HTTP/2 request body across multiple frames so that only a partial body is inspected before reaching the backend. The flaw (CWE-444, HTTP request smuggling) affects only ALB target groups serving HTTP/2 traffic with AWS WAF enabled, and lets attackers slip malicious payloads past WAF managed rules. No public exploit identified at time of analysis and it is not on CISA KEV; AWS scores it 7.9 (CVSS 4.0) with impact falling on the protected backend rather than the ALB itself.

WAF inspection bypass in Amazon CloudFront (with AWS WAF enabled) lets remote actors smuggle malicious request bodies past managed rule inspection by fragmenting the HTTP/2 request body across frames so only a partial body is examined. The flaw (CWE-444, request smuggling) defeats the protective security control rather than CloudFront itself, allowing attacks the WAF would normally block to reach the protected origin. AWS remediated it server-side with no customer action required; there is no public exploit identified at time of analysis and it is not listed in CISA KEV.

HTTP request/response smuggling in nghttpx (the reverse proxy component of nghttp2 through 1.69.0) allows unauthenticated remote attackers to poison shared backend keep-alive connections by crafting an HTTP/1.1 Upgrade request that simultaneously carries a Content-Length header and body. When nghttpx forwards this ambiguous message to a backend and re-adds Connection and Upgrade headers while passing Content-Length verbatim, a backend that resolves the parsing ambiguity in the attacker's favor treats the body as a separate, attacker-controlled HTTP request - enabling cross-client response-queue poisoning. A publicly available proof-of-concept exploit exists; no CISA KEV listing at time of analysis.

HTTP request smuggling in Envoy proxy (versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1) lets remote attackers desynchronize HTTP/1 upstream connections by sending an HTTP/3 downstream request that is transport-complete (HEADERS with FIN) yet declares a nonzero Content-Length, leaving the translated HTTP/1 request with unresolved body debt. When the HTTP/1 origin replies before reading the body and keeps the connection reusable, the start of Envoy's next upstream request is consumed as the prior request's body, and the remainder is parsed by the origin as a separate, attacker-controlled request. This was demonstrated as a route-bypass: a directly denied /pwn was served to a second downstream stream as a backend-parsed GET /pwn, with no public exploit identified at time of analysis and no CISA KEV listing.

HTTP request smuggling in IBM WebSphere Application Server 8.5/9.0 and WebSphere Application Server Liberty 17.0.0.3 through 26.0.0.6 allows unauthenticated remote attackers to bypass security controls, spoof identities, escalate privileges, and access sensitive information. IBM has released fixes and SSVC currently rates exploitation as 'none' with EPSS at 0.35% (27th percentile), but the CVSS 9.1 rating and total technical impact warrant prompt patching given the product's enterprise footprint. No public exploit identified at time of analysis.

HTTP/2 request smuggling in PHP Standard Library (PSL) versions 6.1.0, 6.1.1, and 6.2.0 lets remote unauthenticated clients desynchronize stream boundaries in Psl\H2\ServerConnection by sending DATA frame totals that disagree with the declared content-length header. Only applications that consume the low-level H2 server connection directly to accept untrusted traffic are exposed; high-level PSL APIs are unaffected. No public exploit identified at time of analysis, and the maintainers state the issue was found during internal review prior to public exploitation.

HTTP request smuggling in Tinyproxy through 1.11.3 allows remote unauthenticated attackers to desynchronize the proxy and its backend by sending requests with multiple Content-Length headers having differing values. Because Tinyproxy forwards all duplicate Content-Length headers while parsing only the first value, downstream servers may interpret request boundaries differently, enabling cache poisoning, access control bypass, and request hijacking. No public exploit identified at time of analysis, but the underlying primitive is well documented and the upstream commit 364cdb6 clearly demonstrates the parsing flaw.

HTTP request smuggling in Tinyproxy through 1.11.3 lets remote unauthenticated attackers desynchronize the proxy and backend by sending requests carrying both Content-Length and Transfer-Encoding: chunked headers. Tinyproxy forwards both headers verbatim while parsing the body using Content-Length, producing a classic CL.TE desync that enables cache poisoning, access control bypass, and request hijacking against the backend. No public exploit identified at time of analysis, though VulnCheck has published an advisory and the upstream issue/PR describe the bug in detail.

Authentication bypass in Tinyproxy through 1.11.3 lets unauthenticated remote attackers reach the internal statistics page and smuggle transparent-proxy requests by forging or port-manipulating the HTTP Host header, because stathost detection used a brittle strcmp against the configured hostname. The flaw is a CWE-444 request-interpretation inconsistency reported by VulnCheck; no public exploit identified at time of analysis, though the upstream fix (commit 09312a1) and a detailed PR diff are publicly available, making a working PoC trivial to reconstruct.

Authentication bypass in vLLM versions 0.3.0 through 0.21.x allows remote unauthenticated attackers to reach OpenAI-compatible API endpoints without supplying the configured VLLM_API_KEY by injecting URL-special characters into the HTTP Host header. The flaw stems from vLLM's AuthenticationMiddleware reconstructing the request URL via starlette's URL(scope) - which trusts an unsanitized Host value - while FastAPI routing uses the raw HTTP path, producing a mismatch the attacker controls. No public exploit identified at time of analysis, but x41-dsec disclosed full technical details and a vendor-released patch is available in 0.22.0.

HTTP/2-to-HTTP/1.1 request smuggling in swift-nio-http2 (versions prior to 1.44.1) allows unauthenticated remote attackers to inject arbitrary HTTP headers or smuggle entire requests to backend systems in reverse-proxy configurations. The codecs HTTP2FramePayloadToHTTP1ServerCodec and HTTP2ToHTTP1ServerCodec fail to strip CR, LF, or NUL control characters from HTTP/2 pseudo-header values such as :path and :authority before writing them into the HTTP/1.1 output, enabling the binary-safe HTTP/2 layer to act as a covert channel for control characters that become structural delimiters in HTTP/1.1. No public exploit has been identified at time of analysis, but this vulnerability is a direct extension of two prior confirmed CRLF injection flaws in the same library family (GHSA-7fj7-39wj-c64f and GHSA-cq87-8r7h-962v), indicating a recurring pattern that lowers the technical barrier for exploitation.

HTTP request smuggling in Netty's HttpObjectDecoder (netty-codec-http) allows unauthenticated remote attackers to manipulate request-boundary parsing in pipelined or multiplexed deployments by injecting non-CRLF ISO control characters (NUL, SOH, STX, etc.) before the HTTP request-line. Affected are all Netty releases prior to 4.1.135.Final and 4.2.15.Final; both branches have vendor-confirmed patches. No public exploit code has been identified and EPSS is 0.04% (12th percentile), indicating low current exploitation likelihood, though the attack surface expands significantly in architectures fronted by proxies or load balancers that strip or interpret those control bytes differently than Netty does.

HTTP request smuggling in Kong Gateway Enterprise (3.4, 3.10-3.14 series) enables unauthenticated remote attackers to desynchronize the HTTP/1.1 processing pipeline between Kong and its backend services, achieving high confidentiality and integrity impact against downstream systems. The parsing flaw (CWE-444) exploits ambiguous header interpretation to poison backend request queues, allowing cross-user request hijacking or malicious content injection. Proof-of-concept exploit code exists (CVSS 4.0 E:P), and no active exploitation is confirmed in CISA KEV at time of analysis.

Multipart request smuggling in Spring Framework's MVC and WebFlux components exposes applications to HTTP request manipulation via CWE-444. Unauthenticated remote attackers (AV:N/AC:L/PR:N/UI:N per CVSS) can exploit inconsistent multipart boundary parsing to smuggle malformed HTTP requests, achieving low-integrity impact against affected deployments. No public exploit code and no CISA KEV listing have been identified at time of analysis; however, the zero-prerequisite attack profile and broad version coverage across four major Spring branches (5.3.x, 6.1.x, 6.2.x, 7.0.x) make this relevant to any Java shop running Spring MVC or WebFlux with multipart upload handling enabled.

Header injection via parser differential in daphne before 4.2.2 allows unauthenticated remote attackers to smuggle synthetic headers into the ASGI scope received by Django applications during WebSocket handshake processing. The root cause is that Twisted (which daphne uses to parse inbound HTTP) ignores six specific Unicode bytes as line separators, while autobahn (which daphne feeds for WebSocket negotiation) calls Python's str.splitlines() and recognizes them - causing a single header value to be split into multiple injected header lines. No public exploit has been identified at time of analysis, and CVSS scores this at 3.7 (Low) due to high attack complexity, though real-world severity scales with how heavily the downstream application trusts ASGI-scope headers for security decisions.

HTTP/2 request parsing in Vinyl Cache and Varnish Cache enables backend request desync (HTTP request smuggling), exploitable for cache poisoning, authentication bypass, and information disclosure against affected deployments. Vinyl Cache prior to 9.0.1 and Varnish Cache prior to 9.0.3, plus legacy pre-split Varnish Cache branches spanning versions 6.0.14 through 8.0.1, are confirmed affected across three distinct CPE lineages. Exploitation is gated behind an explicitly non-default configuration - HTTP/2 must be enabled via the +http2 feature parameter - which substantially limits exposure; no public exploit code and no CISA KEV listing have been identified at time of analysis.

HTTP response smuggling in the Elixir Mint HTTP client library (versions 0.1.0 through before 1.9.0) allows attacker-controlled upstream servers to desynchronize response framing on shared connections by exploiting a non-RFC-compliant Content-Length parser. Mint's parser accepts sign-prefixed integers such as '+0' or '+123' that RFC 7230 forbids, creating a disagreement with RFC-strict fronting proxies about where one HTTP response body ends and the next begins. When Mint reuses connections via keep-alive, pipelining, or pooling across trust boundaries, this parser mismatch can be weaponized to leak bytes from one requester's response into another's stream. No public exploit code has been identified at time of analysis, and no KEV listing exists; a vendor patch (v1.9.0) is available.

HTTP request smuggling in libsoup allows remote unauthenticated attackers to exploit an unsigned-to-signed integer conversion error in the `soup_body_input_stream_read_chunked()` function via a crafted HTTP request. The vulnerability is confined to specific proxy topologies where libsoup operates either behind or in front of a non-libsoup HTTP intermediary, and successful exploitation can result in authentication bypass, web cache poisoning, or unauthorized access. No public exploit has been identified at time of analysis and this CVE is not listed in CISA KEV, but the integrity and confidentiality impacts warrant urgent attention in any affected mixed-proxy deployment.

Path prefix stripping in Hono's app.mount() API exposes mounted sub-applications to incorrect routing due to a raw-vs-decoded URL path inconsistency, potentially allowing unauthenticated remote attackers to reach unintended endpoints and disclose protected information. All Hono versions prior to 4.12.21 are affected across every supported JavaScript runtime. No public exploit or CISA KEV listing exists at time of analysis; however, the CVSS vector AV:N/AC:L/PR:N/UI:N and the 'Information Disclosure / Request Smuggling' classification make this a meaningful priority for any deployment that relies on mount-prefix path logic for access segregation.

Host header injection in Starlette prior to version 1.0.1 allows unauthenticated remote attackers to cause `request.url.path` to differ from the actual ASGI scope path used for routing, enabling bypass of middleware and endpoint security controls that rely on `request.url` rather than the raw scope. Any application enforcing path-based ACLs, authentication gates, or WAF-style filters through `request.url` is affected, as a crafted Host header can make the URL appear to address a permitted path while the real route differs. This issue carries CVSS 6.5 (AV:N/AC:L/PR:N/UI:N); no public exploit has been identified at time of analysis and it is not listed in CISA KEV.

Remote code execution and denial of service in IBM Web Server Plug-ins for WebSphere Application Server and WebSphere Liberty 8.5 and 9.0 stem from improper input validation (CWE-444 HTTP Request Smuggling). Unauthenticated network attackers can send crafted requests that desynchronize the plug-in's request parsing, potentially achieving full compromise of the application tier. No public exploit identified at time of analysis, and EPSS remains low (0.06%), but the vendor confirms a patch and CISA SSVC rates the technical impact as total with automatable exploitation.

HTTP request smuggling in IBM Web Server Plug-ins for WebSphere Application Server and WebSphere Liberty 8.5 and 9.0 allows remote unauthenticated attackers to send specially crafted requests that desynchronize front-end and back-end HTTP parsing. Successful exploitation enables cache poisoning, security control bypass, and limited disclosure or modification of data passing through the plug-in, with a CVSS 7.5 reflecting a Changed scope and high confidentiality impact. There is no public exploit identified at time of analysis, EPSS is low at 0.05% (15th percentile), and CISA SSVC marks exploitation status as none.

HTTP request smuggling in Netty's HttpRequestDecoder allows remote unauthenticated attackers to inject arbitrary HTTP requests by sending malformed Transfer-Encoding headers (specifically 'Transfer-Encoding: chunked, identity'). When Netty is deployed behind a proxy that forwards such requests without rejection, an attacker can smuggle a second request inside the body of the first, bypassing security controls and accessing unintended resources. The vulnerability is confirmed by public proof-of-concept code demonstrating successful parsing of injected requests.

HTTP response desynchronization in Netty's HttpClientCodec (netty-codec-http 4.1.x through 4.1.132.Final and 4.2.0.Alpha1 through 4.2.12.Final) lets a malicious or misbehaving server cause one request's response body to be parsed as another's. Because the codec polls its request queue once per inbound response — including for informational 1xx — a pipelined GET+HEAD sequence preceded by a 103 mispairs the HEAD with the GET's 200, leaving GET entity bytes on the wire so the following response is parsed from the wrong offset. Rated CVSS 9.1 (I:H/A:H), publicly available exploit code exists (a vendor PoC ships in the advisory), though EPSS is very low (0.04%) and it is not on CISA KEV.

HTTP request smuggling in Netty's netty-codec-http (HttpObjectDecoder) lets remote attackers desynchronize message boundaries by sending an HTTP/1.0 request carrying both Transfer-Encoding: chunked and Content-Length. Netty's anti-smuggling sanitization that strips the conflicting Content-Length header only runs for HTTP/1.1, so on HTTP/1.0 Netty parses the body as chunked while leaving Content-Length intact for any downstream Content-Length-first proxy, which then treats trailing chunk bytes as a new request. Publicly available exploit code exists (a working EmbeddedChannel PoC test), but EPSS is very low (0.03%, 8th percentile) and it is not in CISA KEV.

HTTP request smuggling in Netty's chunk size parser allows remote unauthenticated attackers to inject arbitrary HTTP requests by exploiting integer overflow in the hexadecimal chunk size parsing logic. The HttpObjectDecoder.getChunkSize method accumulates the chunk size without proper overflow validation, enabling an attacker to craft a malicious chunk size header that wraps around to a valid size, causing Netty to misinterpret the request boundary and parse injected requests as separate legitimate requests. Publicly available proof-of-concept demonstrates successful parsing of an injected GET request within a chunked POST body, with CVSS score 6.5 (network-accessible, low complexity, no authentication required).

HTTP Request Smuggling in Gazelle (Perl web server) versions through 0.49 enables attackers to smuggle malicious requests through reverse proxies by exploiting incorrect header precedence. Gazelle violates RFC 7230 by prioritizing Content-Length over Transfer-Encoding: chunked when both headers are present, allowing desynchronization between front-end proxies and the backend server. SSVC framework indicates the vulnerability is automatable with partial technical impact, while CVSS 7.5 reflects network-accessible unauthenticated exploitation with high integrity impact. A vendor patch is available via CPANSec.

HTTP request smuggling in Starlet through version 0.31 allows remote unauthenticated attackers to bypass header validation by exploiting incorrect precedence of Content-Length over Transfer-Encoding headers. The vulnerability violates RFC 7230 section 3.3.3, which mandates that Transfer-Encoding must take precedence when both headers are present. An attacker positioned between a client and Starlet-based backend can craft malicious requests that are interpreted differently by a front-end reverse proxy and the Starlet server, enabling request smuggling attacks with integrity impact.

HTTP request smuggling in mtrudel bandit before version 1.11.0 allows unauthenticated attackers to bypass edge security controls when the application sits behind a proxy that interprets duplicate Content-Length headers differently. The vulnerability stems from Bandit accepting only the first Content-Length header while proxies may use the last value, causing request framing desynchronization that enables smuggling past WAF rules, path-based ACLs, rate limiting, and audit logging. CVSS 6.3 (AV:N/AC:L/AT:P) indicates network-accessible exploitation with some attack timing complexity; no public exploit code or active KEV listing identified at analysis time, but RFC 9112 non-compliance creates a known attack pattern.

HTTP request smuggling in Starman, the preforking Perl PSGI/Plack web server, affects all releases before 0.4018 due to incorrect header precedence (CWE-444): when a request carries both Content-Length and Transfer-Encoding: chunked, Starman honors Content-Length instead of chunked encoding, violating RFC 7230 §3.3.3. When Starman sits behind a front-end reverse proxy that resolves the ambiguity differently, an attacker can desynchronize the two parsers to smuggle requests, poison the request queue, and capture or manipulate other users' traffic. There is no public exploit identified at time of analysis, EPSS is very low (0.02%), and CISA SSVC records exploitation status as none, but a vendor patch is available in version 0.4018.

HTTP request smuggling in Apache Pony Mail (Lua implementation) enables remote unauthenticated attackers to achieve complete admin account takeover with critical impact across confidentiality, integrity, and availability. This affects all versions of the retired Lua codebase - Apache has abandoned support with no patch planned, recommending migration to alternative solutions. CVSS 9.8 critical severity reflects trivial network-based exploitation requiring no authentication or user interaction.

HTTP request smuggling in libsoup's header parsing enables unauthenticated remote attackers to inject malformed requests containing multiple conflicting Content-Length headers, potentially bypassing security controls or poisoning shared connection state in two-tier deployments. The flaw resides in soup_message_headers_append_common() within libsoup/soup-message-headers.c, which blindly appends header values without validating for duplicate or contradictory Content-Length fields - a direct violation of RFC 7230. No active exploitation has been confirmed (not in CISA KEV), EPSS stands at 0.03% (8th percentile), and SSVC rates exploitation as none with partial technical impact, placing this firmly in the low-urgency tier despite its network-accessible attack vector.

HTTP request smuggling in HCL BigFix Service Management allows remote unauthenticated attackers to exploit HTTP parsing inconsistencies between front-end and back-end servers, potentially leading to limited information disclosure through cache poisoning or request hijacking attacks. The vulnerability has a CVSS score of 3.7 with low confidentiality impact but no direct availability or integrity impact.

HTTP request smuggling in Eclipse Jetty's HTTP/1.1 parser lets remote unauthenticated attackers desynchronize front-end/back-end request boundaries by abusing quoted-string chunk extensions. Jetty incorrectly terminates chunk-extension parsing at a CRLF located inside an unterminated quoted-string (e.g. `1;a="`) rather than rejecting it, so attacker-controlled bytes are reinterpreted as a second, smuggled request on the same TCP connection. Publicly available exploit code exists (a working Python PoC ships in the GHSA advisory), though EPSS is very low (0.03%, 9th percentile) and the issue is not on CISA KEV.

HTTP request smuggling in Apache Tomcat 7.x through 11.x permits unauthenticated remote attackers to manipulate request routing and bypass security controls via malformed chunk extension processing. Exploitation enables header injection, cache poisoning, and request routing manipulation without code execution. Affects Tomcat 7.0.0-7.0.109, 8.5.0-8.5.100, 9.0.0.M1-9.0.115, 10.1.0-M1-10.1.52, and 11.0.0-M1-11.0.18. No public exploit identified at time of analysis. Low observed exploitation activity (EPSS 0.02%).

HTTP request smuggling and denial of service in Tinyproxy through 1.11.3 allows unauthenticated remote attackers to cause backend worker exhaustion and bypass request inspection controls. The vulnerability stems from case-sensitive Transfer-Encoding header parsing that violates RFC 7230, enabling attackers to send 'Transfer-Encoding: Chunked' (capitalized) to desynchronize Tinyproxy's request state from RFC-compliant backends like Node.js and Nginx. No public exploit identified at time of analysis, though EPSS data not available and technical details are publicly documented in GitHub issue #604. Authentication requirements not confirmed from available data, but CVSS vector indicates network-accessible attack requiring no privileges.

Apache Traffic Server versions 9.0.0-9.2.12 and 10.0.0-10.1.1 are vulnerable to HTTP request smuggling through malformed chunked transfer encoding, allowing attackers to bypass security controls and smuggle malicious requests. The vulnerability stems from improper parsing of chunked messages (CWE-444: Inconsistent Interpretation of HTTP Requests) and affects all deployments using these versions as reverse proxies or intermediaries. Apache has released patched versions 9.2.13 and 10.1.2; no public exploit code or active exploitation has been reported at the time of analysis.

IBM Verify Identity Access and Security Verify Access versions 10.0 through 10.0.9.1 and 11.0 through 11.0.2 allow unauthenticated remote attackers to access sensitive information through HTTP request smuggling via inconsistent interpretation of HTTP requests by a reverse proxy. The vulnerability affects both container and non-container deployments and has a CVSS score of 5.3 with confirmed vendor patch availability.

Remote attackers can access sensitive information in IBM Verify Identity Access Container 11.0-11.0.2, IBM Security Verify Access Container 10.0-10.0.9.1, and their non-containerized counterparts through HTTP request smuggling. The vulnerability exploits inconsistent HTTP request interpretation between the application and its reverse proxy, allowing unauthenticated remote access to restricted data with low attack complexity.

HTTP Request Smuggling in cpp-httplib prior to 0.40.0 allows remote attackers to inject arbitrary HTTP requests on HTTP/1.1 keep-alive connections by embedding malicious request data in the body of GET requests that the static file handler does not consume. The unread body bytes remain on the TCP stream and are interpreted as a new request, enabling information disclosure and request manipulation without authentication or user interaction.

HTTP request smuggling in Undertow (the embedded web server underpinning JBoss EAP, Red Hat Data Grid, and Apache Camel for Spring Boot) allows remote unauthenticated attackers to bypass front-end security controls by prepending whitespace to header lines. Undertow strips leading spaces from the first header line in violation of RFC 7230, creating a parser discrepancy between upstream proxies and the application server. No public exploit identified at time of analysis, and EPSS sits at 0.13% (32nd percentile), but the CVSS 9.1 and broad Red Hat middleware exposure make this a high-value target for chained attacks.

HTTP request smuggling in Undertow allows remote unauthenticated attackers to send `\r\r\r` as a header block terminator, which can desynchronize parsing when Undertow sits behind specific intermediaries such as older Apache Traffic Server or Google Cloud Classic Application Load Balancer. The flaw affects numerous Red Hat distributions of Undertow (JBoss EAP 7/8, Data Grid 8, Fuse 7, Camel for Spring Boot 4, RHEL 8/9/10) and carries a CVSS 9.1, though EPSS is only 0.04% and there is no public exploit identified at time of analysis.

HTTP request smuggling in Red Hat Undertow allows remote unauthenticated attackers to bypass front-end security controls by exploiting parsing discrepancies between Undertow and upstream proxies when handling crafted header names. The flaw (CWE-444) affects Undertow embedded in multiple Red Hat products including JBoss EAP 7/8, Data Grid 8, Fuse 7, and Apache Camel for Spring Boot 4, with Red Hat issuing patches via RHSA-2026:25125 and RHSA-2026:25126. There is no public exploit identified at time of analysis and EPSS is low (0.10%), but CVSS 9.1 and SSVC 'total' technical impact warrant prompt patching of internet-facing deployments.

CVE-2026-33870 is a security vulnerability (CVSS 7.5). High severity vulnerability requiring prompt remediation.

An HTTP Request/Response Smuggling vulnerability exists in visualfc liteide due to inconsistent interpretation of HTTP requests in the HTTP parser component (http_parser.C), classified under CWE-444. This affects liteide versions before x38.4, allowing attackers to exploit the qjsonrpc HTTP parser module to smuggle malicious requests. An attacker could leverage this vulnerability to perform request smuggling attacks, potentially leading to cache poisoning, session hijacking, or information disclosure depending on the deployment context and HTTP intermediaries involved.

CVE-2026-29057 is a security vulnerability (CVSS 6.5) that allows request smuggling. Remediation should follow standard vulnerability management procedures. Vendor patch is available.

A critical HTTP Request Smuggling vulnerability exists in Erlang OTP's inets httpd module that allows attackers to desynchronize front-end and back-end servers by exploiting inconsistent Content-Length header parsing. The vulnerability affects Erlang OTP versions from 17.0 through 28.4.0 (inets 5.10 through 9.6.0) and enables attackers to bypass security controls, potentially poisoning web caches or accessing unauthorized resources. While not currently listed in CISA KEV or showing high EPSS scores, the vulnerability has a CVSS 4.0 score of 7.0 and could lead to significant security boundary violations in production environments using affected Erlang-based web services.