HTTP Request Smuggling

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.

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 allows response body misattribution across pipelined requests when servers send 1xx informational responses. When a client pipelines GET and HEAD requests and the server responds with 103 Early Hints followed by 200 responses, the codec incorrectly pairs the HEAD request with the GET's 200 response, causing the GET response body to remain on the stream and corrupt subsequent response parsing. This enables request smuggling and information disclosure attacks. CVSS 7.3 with network-accessible, unauthenticated attack vector. Publicly available exploit code exists (PoC in GitHub advisory). EPSS data not provided, not listed in CISA KEV. Vendor-released patches available in Netty 4.1.133.Final and 4.2.13.Final.

HTTP request smuggling in Netty's HttpObjectDecoder allows remote attackers to bypass Content-Length sanitization for HTTP/1.0 requests carrying both Transfer-Encoding: chunked and Content-Length headers. Netty strips the conflicting Content-Length only for HTTP/1.1, leaving it intact for HTTP/1.0, causing downstream proxies that prioritize Content-Length to misinterpret message boundaries and process attacker-injected payloads as separate requests. Confirmed actively exploited (CISA KEV not indicated, but reproducible POC provided). Affects Netty 4.2.0–4.2.12 and 4.1.0–4.1.132.

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.

Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per RFC 7230 3.3.3, Transfer-Encoding must take precedence. An attacker could exploit this to smuggle malicious HTTP requests via a front-end reverse proxy.

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.

A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic. The soup_message_headers_append_common() function in libsoup/soup-message-headers.c unconditionally appends each header value without validating for duplicate or conflicting Content-Length fields. This allows an attacker to send HTTP requests containing multiple Content-Length headers with differing values.

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 versions 9.4.0-12.1.6 allows remote unauthenticated attackers to inject smuggled requests via malformed chunked transfer encoding. The HTTP/1.1 parser incorrectly terminates chunk extension parsing at \r\n inside quoted strings instead of treating this as a protocol violation, enabling 'funky chunks' smuggling techniques. This affects all major Jetty version branches (9.4.x, 10.0.x, 11.0.x, 12.0.x, and 12.1.x). EPSS data not available, no confirmed active exploitation (CISA KEV negative), but publicly documented attack techniques exist.

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.

Undertow's improper handling of HTTP requests with leading whitespace in header lines enables remote, unauthenticated request smuggling attacks (CWE-444) against Red Hat middleware and enterprise products. Attackers can exploit this HTTP standard violation to bypass security controls, access restricted data, or poison web caches across a wide deployment base including JBoss EAP 7/8, Red Hat Fuse 7, Data Grid 8, and RHEL 8/9/10 distributions. The CVSS score of 8.7 with changed scope (S:C) and high attack complexity (AC:H) indicates significant impact potential, though no public exploit identified at time of analysis.

Undertow HTTP request smuggling via malformed header terminator allows remote unauthenticated attackers to bypass security controls and manipulate web requests through vulnerable proxies including older Apache Traffic Server and Google Cloud Classic Application Load Balancer. With CVSS 8.7 (High/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N), the vulnerability affects multiple Red Hat product lines including JBoss EAP 7 and 8, Fuse 7, Data Grid 8, and RHEL 8-10 distributions. No public exploit identified at time of analysis, though the attack vector is network-accessible and requires no authentication.

Undertow header parsing discrepancies enable HTTP request smuggling attacks against Red Hat middleware and enterprise platforms, allowing remote unauthenticated attackers to bypass security controls and access unauthorized resources. The vulnerability affects multiple Red Hat products including JBoss Enterprise Application Platform 7 and 8, Data Grid 8, Fuse 7, Single Sign-On 7, and Enterprise Linux 8, 9, and 10 distributions. With a CVSS score of 8.7 and changed scope (S:C), attackers can exploit inconsistent header interpretation between Undertow and upstream proxies to smuggle malicious requests past authentication and authorization mechanisms, achieving high confidentiality and integrity impact without requiring authentication.

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.

An inconsistent interpretation of http requests ('http request smuggling') vulnerability in Fortinet FortiOS 7.6.0, FortiOS 7.4.0 through 7.4.9, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4.3 through 6.4.16 may allow an unauthenticated attacker to smuggle an unlogged http request through the firewall policies via a specially crafted header [CVSS 5.8 MEDIUM]

HTTP request smuggling in libsoup allows remote attackers to exploit non-compliant chunk header parsing by injecting malformed requests with LF-only line endings instead of proper CRLF formatting. Without requiring authentication, an attacker can cause libsoup to interpret multiple HTTP requests from a single network message, potentially leading to information disclosure. No patch is currently available for this vulnerability.

HTTP request smuggling in H3 framework versions before 1.15.5 allows remote attackers to bypass security controls by exploiting improper case-sensitive validation of the Transfer-Encoding header. The vulnerability enables attackers to inject malicious requests that diverge between client and server parsing, potentially leading to cache poisoning, session hijacking, or other attacks. Public exploit code exists for this vulnerability.

lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. Rated medium severity (CVSS 6.9), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.

Http4s is a Scala interface for HTTP services. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

An HTTP Request Smuggling [CWE-444] vulnerability in the Authentication portal of WatchGuard Fireware OS allows a remote attacker to evade request parameter sanitation and perform a reflected. Rated medium severity (CVSS 6.9), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Netty is an asynchronous event-driven network application framework for development of maintainable high performance protocol servers and clients. Rated low severity (CVSS 2.9), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

Eventlet is a concurrent networking library for Python. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.

Akamai Ghost before 2025-07-21 allows HTTP Request Smuggling via an OPTIONS request that has an entity body, because there can be a subsequent request within the persistent connection between an. Rated medium severity (CVSS 4.0), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

An issue was discovered in Akamai Ghost, as used for the Akamai CDN platform before 2025-03-26. Rated medium severity (CVSS 4.0), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

EspoCRM is a web application with a frontend designed as a single-page application and a REST API backend written in PHP. Rated medium severity (CVSS 4.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available.

Spring Cloud Gateway Server forwards the X-Forwarded-For and Forwarded headers from untrusted proxies. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

A request smuggling vulnerability identified within Pingora’s proxying framework, pingora-proxy, allows malicious HTTP requests to be injected via manipulated request bodies on cache HITs, leading to. Rated high severity (CVSS 7.4), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

A flaw in Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n`. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

A request smuggling vulnerability existed in the Google Cloud Classic Application Load Balancer due to improper handling of chunked-encoded HTTP requests. Rated high severity (CVSS 8.7), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Varnish Cache before 7.6.3 and 7.7 before 7.7.1, and Varnish Enterprise before 6.0.13r14, allow client-side desync via HTTP/1 requests, because the product incorrectly permits CRLF to be skipped to. Rated medium severity (CVSS 5.4), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

Radware Cloud Web Application Firewall (WAF) before 2025-05-07 allows remote attackers to bypass firewall filters by placing random data in the HTTP request body when using the HTTP GET method. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

h11 is a Python implementation of HTTP/1.1. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

An issue in OpenResty lua-nginx-module v.0.10.26 and before allows a remote attacker to conduct HTTP request smuggling via a crafted HEAD request. Rated high severity (CVSS 7.7), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.

An issue in croogo v.3.0.2 allows an attacker to perform Host header injection via the feed.rss component. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

When using the ch-go library, under a specific condition when the query includes a large, uncompressed malicious external data, it is possible for an attacker in control of such data to smuggle. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable. No vendor patch available.

Apache Traffic Server allows request smuggling if chunked messages are malformed.2.0 through 9.2.9, from 10.0.0 through 10.0.4. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

React Router is a multi-strategy router for React bridging the gap from React 18 to React 19. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Varnish Cache before 7.6.2 and Varnish Enterprise before 6.0.13r10 allow client-side desync via HTTP/1 requests. Rated medium severity (CVSS 5.4), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.

Gunicorn version 21.2.0 does not properly validate the value of the 'Transfer-Encoding' header as specified in the RFC standards, which leads to the default fallback method of 'Content-Length,'. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

HTTP Request Smuggling vulnerability in netease-youdao/qanything version 1.4.1 allows attackers to exploit inconsistencies in the interpretation of HTTP requests between a proxy and a server. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

In JetBrains Ktor before 3.1.1 an HTTP Request Smuggling was possible. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

A critical HTTP Request/Response Smuggling vulnerability (CWE-444) in ithewei libhv library versions up to 1.3.3 allows attackers to manipulate HTTP request interpretation between frontend and backend servers. With a CVSS 4.0 score of 10.0, this vulnerability requires no authentication or user interaction and can be exploited remotely with low complexity. HTTP smuggling attacks can bypass security controls, poison web caches, hijack user sessions, and enable cross-site scripting, making this particularly dangerous in environments using libhv as a reverse proxy or HTTP server component.

In Perfex Crm < 3.2.1, an authenticated attacker can send a crafted HTTP POST request to the affected upload_sales_file endpoint. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

A flaw was found in OpenShift Service Mesh 2.6.3 and 2.5.6. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

Puma is a web server for Ruby/Rack applications built for parallelism. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.