CVE-2026-33433
HIGHCVSS v3.1: 8.8 · EPSS: 0.0045 (35.9 percentile)
Source data as of:
At a glance
- Severity
- HIGH
- CVSS
- 8.8 v3.1 · NVD
- EPSS
- 0.0045 (35.9 percentile) · FIRST.org
- CISA KEV
- No
- Attack conditions (CVSS vector)
- NetworkNo user interaction · Source: NVD Vector
- Affected vendors
- traefik
- Published
- 2026-03-27 · Modified: 2026-06-30
- References
- Jump to references (8)
CVSS / EPSS / KEV
Source — CVSS: NVD · EPSS: FIRST.org · KEV: CISA. Data & Sources
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.
References
Reference URLs as listed by NVD, grouped by a mechanical match on the link's host/pattern. Labels describe the link type only.
- Patch https://github.com/traefik/traefik/releases/tag/v2.11.42
- Patch https://github.com/traefik/traefik/releases/tag/v3.6.11
- Patch https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3
- Vendor advisory https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
- Distro https://access.redhat.com/errata/RHSA-2026:10175
- Distro https://access.redhat.com/security/cve/CVE-2026-33433
- Distro https://bugzilla.redhat.com/show_bug.cgi?id=2452289
- Distro https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33433.json