OESA-2026-1555

A C++11 single-file header-only cross platform HTTP/HTTPS library. It's extremely easy to setup. Just include httplib.h file in your code!

Security Fix(es):

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, when a request handler throws a C++ exception and the application has not registered a custom exception handler via setexceptionhandler(), the library catches the exception and writes its message directly into the HTTP response as a header named EXCEPTIONWHAT. This header is sent to whoever made the request, with no authentication check and no special configuration required to trigger it. The behavior is on by default. A developer who does not know to opt in to setexception_handler() will ship a server that leaks internal exception messages to any client. This vulnerability is fixed in 0.35.0.(CVE-2026-28434)

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, cpp-httplib (httplib.h) does not enforce Server::setpayloadmax_length() on the decompressed request body when using HandlerWithContentReader (streaming ContentReader) with Content-Encoding: gzip (or other supported encodings). A small compressed payload can expand beyond the configured payload limit and be processed by the application, enabling a payload size limit bypass and potential denial of service (CPU/memory exhaustion). This vulnerability is fixed in 0.35.0.(CVE-2026-28435)

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.37.0, cpp-httplib uses std::regex (libstdc++) to parse RFC 5987 encoded filename* values in multipart Content-Disposition headers. The regex engine in libstdc++ implements backtracking via deep recursion, consuming one stack frame per input character. An attacker can send a single HTTP POST request with a crafted filename* parameter that causes uncontrolled stack growth, resulting in a stack overflow (SIGSEGV) that crashes the server process. This issue has been patched in version 0.37.0.(CVE-2026-29076)