high8.8
CVE-2026-33433
Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/traefik/traefik/v2 | < 2.11.42 | 2.11.42 |
| go | github.com/traefik/traefik/v3 | >= 3.0.0-beta1, < 3.6.11 | 3.6.12 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Traefik | Traefik | before 2.11.42 from 3.0.0 before 3.6.12 Version 3.7.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-qr99-7898-vr7c
- https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
- https://nvd.nist.gov/vuln/detail/CVE-2026-33433
- 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/errata/RHSA-2026:10175
- 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