CVE-2026-33433

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 v3 8.8 HIGH

8.8^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.8 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/traefik/traefik/releases/tag/v2.11.42	Product Release Notes
https://github.com/traefik/traefik/releases/tag/v3.6.11	Product Release Notes
https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3	Product Release Notes
https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c	Exploit 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

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:traefik:traefik::::::::
	cpe:2.3:a:traefik:traefik::::::::
	cpe:2.3:a:traefik:traefik:3.7.0:ea1::::::
	cpe:2.3:a:traefik:traefik:3.7.0:ea2::::::

History

No history.

Information

Published : 2026-03-27 15:16

Updated : 2026-07-15 02:20

NVD link : CVE-2026-33433

Mitre link : CVE-2026-33433

CVE.ORG link : CVE-2026-33433

JSON object : View

Products Affected

traefik

traefik

CWE

CWE-290

Authentication Bypass by Spoofing

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Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue."}], "lastModified": "2026-07-15T02:20:13.380", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "EDF93D3C-490C-4EC6-A934-8B877C389491", "versionEndExcluding": "2.11.42"}, {"criteria": "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "5CDD2F75-D51B-4443-B0B6-4ED956ADE494", "versionEndExcluding": "3.6.12", "versionStartIncluding": "3.0.0"}, {"criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "7881B288-5141-4508-AB71-3F7586168437"}, {"criteria": "cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "AE5788A2-CCF9-4E87-8B94-133874F99CAE"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}