Authentication Bypass Affecting traefik-fips-2.11 package, versions <2.11.42-r0


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.49% (42nd percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-TRAEFIKFIPS211-15965991
  • published10 Apr 2026
  • disclosed27 Mar 2026

Introduced: 27 Mar 2026

CVE-2026-33433  (opens in a new tab)
CWE-290  (opens in a new tab)

How to fix?

Upgrade Chainguard traefik-fips-2.11 to version 2.11.42-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream traefik-fips-2.11 package and not the traefik-fips-2.11 package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1