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Older Versions of cpp-httplib Library Leak Sensitive Server Information
OESA-2026-1554
Summary
Older versions of the cpp-httplib library can leak sensitive server information to anyone who makes a request. This happens when the server encounters an error and doesn't have a custom error handler set up. To fix this, update to version 0.35.0 or later. Regularly updating your library versions is a good security practice to prevent these kinds of issues.
What to do
- Update cpp-httplib to version 0.37.0-1.oe2403sp3.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | cpp-httplib | <= 0.37.0-1.oe2403sp3 | 0.37.0-1.oe2403sp3 |
Original title
cpp-httplib security update
Original description
A C++11 single-file header-only cross platform HTTP/HTTPS library. It&apos;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 set_exception_handler(), the library catches the exception and writes its message directly into the HTTP response as a header named EXCEPTION_WHAT. 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 set_exception_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::set_payload_max_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)
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 set_exception_handler(), the library catches the exception and writes its message directly into the HTTP response as a header named EXCEPTION_WHAT. 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 set_exception_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::set_payload_max_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)
- https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-28434 Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-28435 Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-29076 Vendor Advisory
Published: 15 Mar 2026 · Updated: 15 Mar 2026 · First seen: 15 Mar 2026