Vulnerability details

Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.

• https://github.com/traefik/traefik/security/advisories/GHSA-9cr8-q42q-g8m7 x_refsource_CONFIRM
• https://github.com/traefik/traefik/pull/13214 x_refsource_MISC
• https://community.traefik.io/t/new-security-update-for-traefik-2-11-2-11-48-3-6-3-6-19-and-3-7-3-7-3/29917 x_refsource_MISC
• https://github.com/traefik/traefik/compare/v3.6.17...v3.6.18 x_refsource_MISC
• https://github.com/traefik/traefik/releases/tag/v3.7.3 x_refsource_MISC
• https://access.redhat.com/security/cve/CVE-2026-53622 x_refsource_MISC
• https://bugzilla.redhat.com/show_bug.cgi?id=2491924 x_refsource_MISC
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53622.json x_refsource_MISC
• https://access.redhat.com/errata/RHSA-2026:62260 vendor-advisoryx_refsource_REDHAT