Vulnerability Description
Mailu is a mail server distributed as a set of Docker images. From Mailu 2.0 until 2024.06.55 and prior to Mailu helm-charts 2.7.3, deployments with PROXY_AUTH_WHITELIST configured but REAL_IP_HEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The proxy_hide_header directive in the nginx template at core/nginx/conf/proxy.conf hid the header from upstream responses but did not overwrite the incoming request value in this configuration. An unauthenticated remote attacker could therefore spoof the trusted proxy identity and bypass authentication. This issue is fixed in Mailu 2024.06.55 and Mailu helm-charts 2.7.3.
CVSS Score
CRITICAL
Related Weaknesses (CWE)
References
- https://github.com/Mailu/Mailu/commit/dffa97cbd889ab208246372ce9c86e99abb27ae9
- https://github.com/Mailu/Mailu/commit/ff4003d045753013470945336448dbd790cac778
- https://github.com/Mailu/Mailu/pull/4070
- https://github.com/Mailu/Mailu/pull/4071
- https://github.com/Mailu/Mailu/releases/tag/2024.06.55
- https://github.com/Mailu/Mailu/security/advisories/GHSA-rfhj-4wcq-74xg
FAQ
What is CVE-2026-85751?
CVE-2026-85751 is a vulnerability with a CVSS score of 9.8 (CRITICAL). Mailu is a mail server distributed as a set of Docker images. From Mailu 2.0 until 2024.06.55 and prior to Mailu helm-charts 2.7.3, deployments with PROXY_AUTH_WHITELIST configured but REAL_IP_HEADER ...
How severe is CVE-2026-85751?
CVE-2026-85751 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-85751?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.