CVE-2026-33433Traefik is an HTTP reverse proxy and load balancer.
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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
- 8.8 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-290
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
traefik traefik traefik:traefik | before 2.11.42; from 3.0.0 before 3.6.12; 3.7.0; 3.7.0 | NVD |
References
- https://github.com/traefik/traefik/releases/tag/v2.11.42product, release-notes
- https://github.com/traefik/traefik/releases/tag/v3.6.11product, release-notes
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3product, release-notes
- https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7cexploit, patch, vendor-advisory
- 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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.