CVE-2026-39858 Traefik: Forwarded alias spoofing top pre-auth decision bypass

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only...

Traefik: Pre-authentication decision bypass due to forwarded alias spoofing

Summary There is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names e.g., X-Forwarded-Proto and does not strip or normalize alias variants that...