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CVE-2026-54763 is an authentication and identity-spoofing flaw in Traefik affecting the BasicAuth, DigestAuth, and ForwardAuth middlewares before versions 2.11.51, 3.6.22, and 3.7.6. The vulnerability arises because Traefik strips canonical hyphenated identity headers before setting its own trusted values, but fails to account for underscore-variant forms of those same headers. In environments where downstream backends normalize underscore and hyphen variants equivalently, a crafted underscore-form header can survive Traefik’s sanitization and be interpreted by the backend as the trusted identity or authorization header. On the ForwardAuth authResponseHeaders path, the attacker-controlled header may also be forwarded in place of the value Traefik intended to set. This can allow spoofing of authenticated user identity or authorization context on requests reaching protected backend services.
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No public exploit code observed for this vulnerability.
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3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A regression/incomplete fix issue in Traefik authentication middleware where underscore-form identity headers such as X_Auth_User can bypass protections, affecting BasicAuth, DigestAuth, and ForwardAuth.
A critical improper authorization vulnerability in Traefik that allows unauthenticated remote attackers to bypass authentication middleware via underscore-variant header injection and spoof identity or authorization context.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.