CVE-2026-33433
Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
- State
- Published
- Severity
- 5.1 Medium
- Published
- Mar 27, 2026
- Updated
- Jul 15, 2026
- Reserved
- Mar 19, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 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 | GitHub_M |
| 3.1 | 7.7 High | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N | redhat-SADP |
Weaknesses
- CWE-290 Authentication Bypass by Spoofing
Affected Products
| Product | Versions |
|---|---|
traefiktraefik |
|
References
- 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-2026-33433vdb-entry
- RHBZ#2452289issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33433.json
- https://access.redhat.com/errata/RHSA-2026:10175vendor-advisory
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