What’s Vulnerable › Vulnerabilities

CVE-2025-66577: cpp-httplib Untrusted HTTP Header Handling: X-Forwarded-For/X-Real-IP Trust

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-12-05 · updated 2026-06-17
• Weakness: CWE-117

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.27.0, a vulnerability allows attacker-controlled HTTP headers to influence server-visible metadata, logging, and authorization decisions. An attacker can supply X-Forwarded-For or X-Real-IP headers which get accepted unconditionally by get_client_ip() in docker/main.cc, causing access and error logs (nginx_access_logger / nginx_error_logger) to record spoofed client IPs (log poisoning / audit evasion). This vulnerability is fixed in 0.27.0.

Affected products

• yhirose cpp-httplib: before 0.27.0 — fixed in 0.27.0

How to fix

Upgrade to a fixed version: yhirose cpp-httplib 0.27.0. Check the vendor advisory for mitigations.

References

• https://github.com/yhirose/cpp-httplib/commit/ac9ebb0ee333ce8bf13523f487bdfad9518a2aff
• https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-gfpf-r66f-5mh2

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