CVE-2026-39858

A flaw was found in Traefik. A remote attacker can exploit an authentication bypass vulnerability by injecting spoofed trust context through unsanitized alias headers. This is due to Traefik's forwarded-header sanitization logic not properly handling alias header names that use underscores instea...

CVE-2026-39858

Traefik vulnerable to a high-severity authentication bypass via forwarded alias headers. The sanitization logic targets only canonical headers (e.g., X-Forwarded-Proto) and does not strip or normalize alias forms using underscores (e.g., X_Forwarded_Proto). When an auth backend normalizes undersc...