Bug 2497551 (CVE-2026-54763)

Summary: CVE-2026-54763 traefik: Traefik: Identity spoofing via improper header handling in authentication middlewares
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik, an HTTP reverse proxy and load balancer. The BasicAuth, DigestAuth, and ForwardAuth middlewares in Traefik do not correctly treat underscore-variant header names. This allows a remote attacker to inject a specially crafted header that bypasses Traefik's security mechanisms. As a result, the attacker can spoof identity or authorization context to the backend, potentially gaining unauthorized access to protected resources.
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Description OSIDB Bzimport 2026-07-06 22:02:53 UTC 
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.