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CVE-2026-33433

Traefik is an HTTP reverse proxy and load balancer.

Published Mar 27, 2026 · updated Jul 15, 2026 · traefik traefik

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 is configured with a non-canonical HTTP header name (e.g., instead of ), 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.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 27, 2026 · NIST NVD

    Detected

    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 is configured with a non-canonical HTTP header name (e.g., instead of ), 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, ov

  2. Jul 15, 2026 · NIST NVD

    Updated

    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 is configured with a non-canonical HTTP header name (e.g., instead of ), 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, ov

Affected

  • cpe traefik/traefikversion unspecified
  • cpe traefik/traefik3.7.0

Sources

  • CVE.orgVulnerability recordCVE-2026-33433

    Official CVE identifier

    cve.org
  • NIST NVDVulnerability recordCVE-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 is configured with a non-canonical HTTP header name (e.g., instead of ), an authenticated attacker can inject their own canonical v

    nvd.nist.gov

References