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.
History

Wed, 04 Mar 2026 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 04 Mar 2026 20:00:00 +0000

Type Values Removed Values Added
Description 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.
Title cpp-httplib's default exception handler leaks e.what() to clients via EXCEPTION_WHAT response header
Weaknesses CWE-200
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-03-04T19:34:30.486Z

Updated: 2026-03-04T20:55:40.320Z

Reserved: 2026-02-27T15:54:05.138Z

Link: CVE-2026-28434

cve-icon Vulnrichment

Updated: 2026-03-04T20:55:35.685Z

cve-icon NVD

Status : Received

Published: 2026-03-04T20:16:19.823

Modified: 2026-03-04T20:16:19.823

Link: CVE-2026-28434

cve-icon Redhat

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