CVE-2026-28434 — cpp-httplib's default exception handler leaks e.what() to clients via EXCEPTION_WHAT response header
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 regi…
Published: 2026-03-04 · CVSS: 5.3 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7