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.
References6
- github.com/Mailu/Mailu/commit/dffa97cbd889ab208246372ce9c86e99a…
- github.com/Mailu/Mailu/commit/ff4003d045753013470945336448dbd79…
- github.com/Mailu/Mailu/pull/4070
- github.com/Mailu/Mailu/pull/4071
- github.com/Mailu/Mailu/releases/tag/2024.06.55
- github.com/Mailu/Mailu/security/advisories/GHSA-rfhj-4wcq-74xg
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 1% percentile: 47 · as of 8 November 2026
- CWE
- CWE-290CWE-807
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.