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Fencer Vulns
medium 5.3

CVE-2025-66577 json

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

published 2025-12-05 11 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-201454

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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.

Patch / fix

  • cpp-httplib_project cpp-httplib 0.27.0
  • yhirose cpp-httplib 0.27.0
  • cpp-httplib Debian 14 0.41.0+ds-3

debian advisories DEBIAN-CVE-2025-66577

  • cpp-httplib Ubuntu 25.10 0.18.7-1ubuntu0.25.10.1
  • cpp-httplib Ubuntu Pro 22.04 LTS 0.10.3+ds-1ubuntu0.1~esm1
  • cpp-httplib Ubuntu Pro 24.04 LTS 0.14.3+ds-1.1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2025-66577

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • cpp-httplib SLES for SAP applications 16.0, SLES 16.0 0.22.0-160000.3.1

suse advisories SUSE-SU-2026:20090-1

  • cpp-httplib openSUSE Leap 16.0 0.22.0-160000.3.1
  • cpp-httplib openSUSE Tumbleweed 0.28.0-1.1

opensuse advisories openSUSE-SU-2026:20056-1openSUSE-SU-2025:15844-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-66577 updated cvss 5.3

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

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-gfpf-r66f-5mh2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

  • yhirose cpp-httplib

Classification

Weakness
  • CWE-117 Improper Output Neutralization for Logs
  • CWE-807 Reliance on Untrusted Inputs in a Security Decision

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.