CVE-2026-33433

8.8 HIGH
Published: March 27, 2026 Modified: April 03, 2026
View on NVD

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/traefik/traefik/releases/tag/v2.11.42
Source: security-advisories@github.com
Product Release Notes
https://github.com/traefik/traefik/releases/tag/v3.6.11
Source: security-advisories@github.com
Product Release Notes
https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3
Source: security-advisories@github.com
Product Release Notes
https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
Source: security-advisories@github.com
Exploit Patch Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
8.8 / 10.0
EPSS (Exploit Probability)
0.0%
5th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

traefik