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CVE-2026-28434

cpp-httplib's default exception handler leaks e.what() to clients via EXCEPTION_WHAT response header

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 0.35.0
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • yhirose cpp-httplib

    fixed in 0.35.0

References 2

GitHub · yhirose/cpp-httplib