CVE-2026-33433 (GCVE-0-2026-33433)
Vulnerability from cvelistv5
Published
2026-03-27 13:49
Modified
2026-03-30 12:00
Severity ?
5.1 (Medium) - CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CWE
  • CWE-290 - Authentication Bypass by Spoofing
Summary
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.
References
Impacted products
Vendor Product Version
traefik traefik Version: < 2.11.42
Version: >= 3.0.0-beta1, < 3.6.11
Version: >= 3.7.0-ea.1, < 3.7.0-ea.3
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