CVE-2026-85751 Mailu: Authentication bypass in header-based proxy authentication via spoofable `X-Forwarded-By` trust

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 PROXYAUTHWHITELIST configured but REALIPHEADER unset trusted a client-controlled X-Forwarded-By header for header-based proxy authentication. The...