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    CVE-2025-66491

    Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.

    Published:Dec 9, 2025
    Last Modified:Jan 2, 2026
    EPS:Dec 9, 2025
    EPSS Score:0.00008
    CVSS Score:5.9

    Affected Products

    Vendor
    Traefik
    Product
    Traefik

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-295 Improper Certificate Validation

    Related CVEs

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    CVE-2026-88011 (CVSS 5.3) — Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12,…
    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