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    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.

    Published:Mar 27, 2026
    Last Modified:Apr 3, 2026
    EPS:Mar 27, 2026
    EPSS Score:0.00014
    CVSS Score:8.8

    Affected Products

    Vendor
    Traefik
    Product
    Traefik

    Exploits

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

    Related CVEs

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    CVE-2026-88009 (CVSS 8.8) — Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.57, and 3.7.13, Traefik accepts …
    CVE-2026-88008 (CVSS 7) — Traefik is an open source HTTP reverse proxy and load balancer. From 2.11.26 until 2.11.57 and 3.7.13, Traefik…
    CVE-2026-88007 (CVSS 9.1) — Traefik is an open source HTTP reverse proxy and load balancer. From 2.11.0 until 2.11.57 and 3.7.13, the HTTP…
    CVE-2026-88004 (CVSS 7) — Traefik is an open source HTTP reverse proxy and load balancer. From 3.2.0 until 3.7.13, Traefik entrypoint de…
    CVE-2026-88879 (CVSS 5.3) — Traefik is an HTTP reverse proxy and load balancer. In Traefik v1.x, v2.x through v2.11.55, and v3.0.0 through…
    CVE-2026-88878 (CVSS 6.9) — Traefik is an HTTP reverse proxy and load balancer. In versions >= v2.8.2 through <= v2.11.55 and >= v3.0.0 th…
    CVE-2026-88877 (CVSS 9.3) — Traefik is a HTTP reverse proxy and load balancer. In versions >= v3.7.0 and <= v3.7.11, the Kubernetes ingres…
    CVE-2026-85596 (CVSS 8.2) — Traefik versions >= v3.7.0 and <= v3.7.10 contain an authentication bypass in the Kubernetes Ingress NGINX pro…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High