CVE-2026-33433
CVE-2026-33433 · Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
This page contains facts from public vulnerability sources. Check the original advisory before updating.
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 5.1 · Medium · EPSS 0.5%
- Published
- Updated
Stack: web
Affected products and versions
traefik
- Versions
- < 2.11.42: Affected
- >= 3.0.0-beta1, < 3.6.11: Affected
- >= 3.7.0-ea.1, < 3.7.0-ea.3: Affected
No fix published
Original sources
- https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
- https://github.com/traefik/traefik/releases/tag/v2.11.42
- https://github.com/traefik/traefik/releases/tag/v3.6.11
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3
- https://access.redhat.com/security/cve/CVE-2026-33433
- https://bugzilla.redhat.com/show_bug.cgi?id=2452289
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33433.json
- https://access.redhat.com/errata/RHSA-2026:10175
- https://nvd.nist.gov/vuln/detail/CVE-2026-33433