CVE-2026-46527

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.

Affected products

Cpp-Httplib

Yhirose Cpp-httplib

< 0.44.0

Fix

Available

CVSS 4.0

8.7 HIGH

CVSS 3.1

7.5 HIGH

EPSS

0.3% (25th percentile)

Weakness

CWE-476

NVD status

Analyzed

Published

2026-05-29

No exploit for CVE-2026-46527 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.