Cpp Httplib

Use-after-free in cpp-httplib's TLS WebSocket client (versions 0.33.0 through 0.50.0) corrupts process memory during ordinary secure WebSocket teardown, causing denial of service in any application that embeds this header-only C++ library with wss:// connections. The SSL/TLS session object is freed in `WebSocketClient::shutdown_and_close` before the WebSocket close frame is transmitted, but the underlying `SSLSocketStream` retains a raw pointer to the freed session and dereferences it during the close handshake. The defect is reachable through three distinct paths - the client destructor, an explicit `shutdown_and_close` call, and the `connect()` reconnect path - meaning routine connection lifecycle events, not crafted adversarial input, reliably trigger the corruption. No KEV listing or standalone public exploit exists at time of analysis; vendor-released patch version 0.50.1 is available.

HTTP response splitting in cpp-httplib 0.49.0 allows an attacker who can influence chunked response trailer values to inject arbitrary headers into the HTTP response stream, potentially forging responses seen by downstream clients. The trailer-writing path in write_content_chunked() is the sole code path in the library that omits the CRLF validation applied by set_header() and every other header-writing function, meaning attacker-controlled CR/LF sequences pass directly to the socket. No public exploit code and no CISA KEV listing have been identified; the fix is confirmed in version 0.50.0 via upstream security advisory GHSA-2r2h-jc8w-w66c.

TLS certificate validation bypass in cpp-httplib's Mbed TLS backend (0.31.0-0.46.1) and wolfSSL backend (0.33.0-0.46.1) lets a man-in-the-middle attacker defeat HTTPS/WSS protection when a client connects to an IP-literal host with verification nominally enabled. SSLClient/Client in HTTPS mode skip certificate chain validation and the WebSocketClient on Mbed TLS skips verification entirely, so an intercepting attacker can present a crafted certificate and read or alter traffic. There is no public exploit identified at time of analysis and it is not listed in CISA KEV; the flaw is fixed in 0.47.0.

HTTP response/header injection in cpp-httplib server versions prior to 0.44.0 allows remote unauthenticated attackers to smuggle CRLF sequences into stored header values, because the is_field_value validity check runs before percent-decoding lets %0D%0A through and expand to literal \r\n. The CVSS 9.9 score with Scope:Changed reflects the ability to influence downstream HTTP components, but no public exploit identified at time of analysis and the issue is not on the CISA KEV list.

Denial of service in cpp-httplib (C++ header-only HTTP/HTTPS library) versions prior to 0.44.0 allows remote unauthenticated attackers to crash server processes by sending an HTTP request with a malformed X-Forwarded-For header. The flaw is reachable only when the application has configured a non-empty trusted-proxy list via Server::set_trusted_proxies(). CVSS 4.0 scores this 8.7 (high) due to network reachability and high availability impact; no public exploit identified at time of analysis and the issue is not listed in CISA KEV.

Denial of service in cpp-httplib before 0.43.4 lets remote unauthenticated attackers crash the server by sending a chunked HTTP request with a negative chunk-size value. Because ChunkedDecoder::read_payload parses the size with std::strtoul(), a value like "-2" wraps to a near-maximum unsigned integer (0xFFFFFFFFFFFFFFFE) that bypasses the library's single guard against ULONG_MAX, driving unbounded memory allocation and a process crash. Publicly available exploit code exists (SSVC: PoC) though it is not in CISA KEV, and EPSS is low at 0.06%.

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.

The cpp-httplib HTTP/HTTPS client library (versions prior to 0.39.0) leaks authentication credentials to arbitrary third-party servers when following cross-origin HTTP redirects. An attacker operating a malicious server can issue a 301/302/307/308 redirect to capture plaintext Basic Auth, Bearer Token, or Digest Auth credentials from the Authorization header. CVSS score of 7.4 reflects high confidentiality and integrity impact with network attack vector and high complexity; no public exploit identified at time of analysis.

cpp-httplib versions before 0.37.2 silently disable TLS certificate validation when following HTTPS redirects through a proxy, allowing attackers to intercept encrypted connections without detection. This affects any application using cpp-httplib as an HTTP client with proxy and redirect following enabled. No active exploitation (not in KEV) or public POC has been reported, with low EPSS probability indicating minimal current threat activity.

cpp-httplib versions prior to 0.37.1 crash when the streaming API receives a malformed Content-Length header from any server, as the library fails to validate or handle exceptions from the underlying string parsing function. An attacker can exploit this denial of service condition by hosting a malicious server, performing a man-in-the-middle attack, or leveraging HTTP redirects to crash any client application using the vulnerable library. Currently no patch is available for this issue.

Remote denial of service in cpp-httplib prior to version 0.37.0 allows unauthenticated attackers to crash server processes by submitting HTTP POST requests with maliciously crafted RFC 5987 filename* parameters that trigger catastrophic backtracking in the regex parser. The vulnerability exploits the recursive stack-based implementation of libstdc++'s regex engine, causing uncontrolled stack growth and stack overflow. Public exploit code exists for this vulnerability.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. [CVSS 7.5 HIGH]

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. [CVSS 5.3 MEDIUM]

cpp-httplib versions prior to 0.30.1 are vulnerable to denial of service attacks due to insufficient validation of decompressed HTTP request body sizes. An unauthenticated remote attacker can send a malicious gzip or brotli-compressed request that decompresses to an arbitrarily large payload in memory, exhausting server resources. Public exploit code exists for this vulnerability, and a patch is available in version 0.30.1 and later.

Cpp-Httplib versions up to 0.30.0 contains a vulnerability that allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack (CVSS 7.5).

A security vulnerability in cpp-httplib (CVSS 5.3) that allows attacker-controlled http headers. Risk factors: public PoC available. Vendor patch is available.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.27.0, a vulnerability allows attacker-controlled HTTP headers to influence server-visible metadata, logging, and authorization decisions. An attacker can inject headers named REMOTE_ADDR, REMOTE_PORT, LOCAL_ADDR, LOCAL_PORT that are parsed into the request header multimap via read_headers() in httplib.h (headers.emplace), then the server later appends its own internal metadata using the same header names in Server::process_request without erasing duplicates. Because Request::get_header_value returns the first entry for a header key (id == 0) and the client-supplied headers are parsed before server-inserted headers, downstream code that uses these header names may inadvertently use attacker-controlled values. Affected files/locations: cpp-httplib/httplib.h (read_headers, Server::process_request, Request::get_header_value, get_header_value_u64) and cpp-httplib/docker/main.cc (get_client_ip, nginx_access_logger, nginx_error_logger). Attack surface: attacker-controlled HTTP headers in incoming requests flow into the Request.headers multimap and into logging code that reads forwarded headers, enabling IP spoofing, log poisoning, and authorization bypass via header shadowing. This vulnerability is fixed in 0.27.0.

CVE-2025-53629 is a Denial of Service vulnerability in cpp-httplib versions prior to 0.23.0 that allows unauthenticated remote attackers to exhaust server memory through maliciously crafted HTTP requests using Transfer-Encoding: chunked headers. The vulnerability has a CVSS score of 7.5 (high severity) with a network-based attack vector requiring no authentication, and is fixed in version 0.23.0. This is a resource exhaustion attack with direct availability impact and no known public exploit code referenced in initial disclosures.

CVE-2025-53628 is a memory exhaustion vulnerability in cpp-httplib versions prior to 0.20.1 that allows unauthenticated remote attackers to cause denial of service by sending HTTP requests with arbitrarily large individual header lines, exploiting the absence of per-line size limits. The vulnerability affects any application using cpp-httplib as a C++ HTTP/HTTPS library component and requires only user interaction (UI:R) to trigger, with high impact across confidentiality, integrity, and availability. No active exploitation in the wild has been confirmed, but the fix availability and related CVE-2025-53629 suggest this was discovered during security review rather than active exploitation.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. In version 0.21.0, when many http headers fields are passed in, the library does not limit the number of headers, and the memory associated with the headers will not be released when the connection is disconnected. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.22.0 contains a patch for the issue.

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

cpp-httplib version v0.17.3 through v0.18.3 fails to filter CRLF characters ("\r\n") when those are prefixed with a null byte. Rated medium severity (CVSS 6.9), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

Versions of the package yhirose/cpp-httplib before 0.12.4 are vulnerable to CRLF Injection when untrusted user input is used to set the content-type header in the HTTP .Patch, .Post, .Put and .Delete. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

cpp-httplib through 0.5.8 does not filter \r\n in parameters passed into the set_redirect and set_header functions, which creates possibilities for CRLF injection and HTTP response splitting in some. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.