cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, When the server has called Server::set_trusted_proxies() with a non-empty trusted-proxy list, an attacker can send an HTTP request that includes an X-Forwarded-For header whose value parses to no valid IP segments. The code path then executes get_client_ip(), which calls front() on an empty std::vector—undefined behavior in C++. On typical implementations this manifests as abnormal process termination (denial of service). With Sanitizers enabled, you get an explicit runtime diagnostic. This vulnerability is fixed in 0.44.0.
History

Mon, 01 Jun 2026 18:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Mon, 01 Jun 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 29 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Yhirose
Yhirose cpp-httplib
Vendors & Products Yhirose
Yhirose cpp-httplib

Fri, 29 May 2026 20:15:00 +0000

Type Values Removed Values Added
Description cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, When the server has called Server::set_trusted_proxies() with a non-empty trusted-proxy list, an attacker can send an HTTP request that includes an X-Forwarded-For header whose value parses to no valid IP segments. The code path then executes get_client_ip(), which calls front() on an empty std::vector—undefined behavior in C++. On typical implementations this manifests as abnormal process termination (denial of service). With Sanitizers enabled, you get an explicit runtime diagnostic. This vulnerability is fixed in 0.44.0.
Title cpp-httplib: Malicious `X-Forwarded-For` Under Trusted-Proxy Configuration Triggers Empty `vector::front()`, Leading to Undefined Behavior and Server Crash
Weaknesses CWE-476
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-05-29T19:18:26.615Z

Updated: 2026-06-01T13:52:30.508Z

Reserved: 2026-05-14T19:12:32.755Z

Link: CVE-2026-46527

cve-icon Vulnrichment

Updated: 2026-06-01T13:52:27.114Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-29T20:16:28.137

Modified: 2026-06-01T18:32:26.637

Link: CVE-2026-46527

cve-icon Redhat

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