VDB
CVE-2026-33433
CVE-2026-33433
PUBLISHED
CVSS 5.099999904632568 MEDIUM
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.
EPSS 0.03% · 8.0th percentile
Risk Scores
CVSS 4.0
5.099999904632568
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
EPSS Score
0.03%
8.0th percentile
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| traefik | traefik | *, *, < 2.11.42 |
| github.com | traefik/traefik/v2 | 0, 0, 0 |
| github.com | traefik/traefik/v3 | 3.0.0-beta1, 3.0.0-beta1, 3.7.0-ea.1 |
Exploit Intelligence
- CIRCL published-proof-of-concept: CVE-2026-33433 (circl-sighting)
- https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c (nist-nvd)
- https://github.com/traefik/traefik/security/advisories/GHSA-67jx-r9pv-98rj (circl)
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2 (circl)
- CIRCL seen: CVE-2026-32695 (circl-sighting)
- CIRCL seen: CVE-2026-32695 (circl-sighting)
- CIRCL seen: CVE-2026-33433 (circl-sighting)
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3 (circl)
- https://github.com/traefik/traefik/releases/tag/v3.6.11 (circl)
- https://github.com/traefik/traefik/releases/tag/v2.11.42 (circl)
…and 9 more exploits
Timeline
- Mar 27, 2026 CVE Published
- Mar 27, 2026 Coalition ESS Score
- Mar 27, 2026 PoC Published
- Mar 27, 2026 PoC Published
- Mar 27, 2026 PoC Published
- Mar 27, 2026 CVE Updated
- Mar 28, 2026 Security Advisory
- Apr 3, 2026 PoC Published
- May 18, 2026 EPSS Score
- May 19, 2026 EPSS Score
- May 20, 2026 EPSS Score
- May 21, 2026 EPSS Score
References
- https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c url
- https://github.com/traefik/traefik/releases/tag/v2.11.42 url
- https://github.com/traefik/traefik/releases/tag/v3.6.11 url
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3 url
- https://github.com/traefik/traefik/security/advisories/GHSA-46wh-3698-f2cx advisory
- https://github.com/traefik/traefik/security/advisories/GHSA-67jx-r9pv-98rj advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-33433 advisory
- https://github.com/traefik/traefik package
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2 url