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CVE-2026-33433

HIGH

8.8

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.

CVE Details

CVSS v3.1 Score8.8

SeverityHIGH

CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredLOW

User InteractionNONE

Published3/27/2026

Last Modified4/3/2026

Sourcenvd

Honeypot Sightings0

Affected Products

traefik:traefik

Weaknesses (CWE)

CWE-290

References

https://github.com/traefik/traefik/releases/tag/v2.11.42(security-advisories@github.com)

https://github.com/traefik/traefik/releases/tag/v3.6.11(security-advisories@github.com)

https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3(security-advisories@github.com)

https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c(security-advisories@github.com)

IOC Correlations

No correlations recorded

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