CVE-2026-54763
CriticalCVSS 10.0Exploitation Probability (EPSS)
Low risk17th percentile - higher than 17% of all known CVEs
Summary
In Traefik prior to versions v2.11.51, v3.6.22, and v3.7.6, the BasicAuth, DigestAuth, and ForwardAuth middlewares fail to strip underscore-variant identity headers that backends normalize to dashed forms. An attacker can inject such a header to spoof identity or bypass authorization.
Risk Assessment
The organization is at risk of unauthorized access to protected resources through identity spoofing, potentially leading to data confidentiality and integrity breaches.
Recommendation
Immediately upgrade Traefik to versions v2.11.51, v3.6.22, or v3.7.6, which include a fix to remove vulnerable underscore-variant headers.
Original NVD description (English source)
Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.