VULNERABILITY INTELLIGENCE

CVE-2026-33433

CVSS score8.8 HIGH
EPSS probability0.49%
CISA KEVNot currently listed
Published2026-03-27
Last modified2026-07-15
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Description

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.

Weakness classification

  • security-advisories@github.com: CWE-290
  • 0b0ca135-0b70-47e7-9f44-1890c2a1c46c: CWE-290

Primary references