CVE-2026-54763: traefik Improper Handling of Case Sensitivity

Vulnerability summary

CVE-2026-54763 is a critical (CVSS 10.0) Improper Handling of Case Sensitivity vulnerability in traefik. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.1% of scored vulnerabilities.

Timeline

1. 06-07-2026
   PublishedVulnerability first disclosed.
2. 08-07-2026
   Last modifiedVulnerability information updated.

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.

• CWE-178Improper Handling of Case SensitivityThe product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
• CWE-290Authentication Bypass by SpoofingThis attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
• CWE-345Insufficient Verification of Data AuthenticityThe product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.