CVE-2026-54763: Traefik: attackers can spoof identity headers

Summary

Traefik, a web server helper, had a security weakness that allowed hackers to fake identity information. This could happen if a hacker reached a protected part of a website. The good news is that this issue has been fixed in newer versions of Traefik.

What to do

No fix is available yet. Check with your software vendor for updates.

Affected software

Vendor	Product	Affected versions
traefik	traefik	< 2.11.51 >= 3.0.0, < 3.6.22 >= 3.7.0, < 3.7.6

Original title

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 heade...

Original description

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.

nvd CVSS4.0 7.8

Vulnerability type

CWE-178

CWE-290

CWE-345