CVE-2026-53622

Vulnerability Description

Traefik is an HTTP reverse proxy and load balancer. Prior to 3.7.3, there is 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 3.7.3.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• https://github.com/traefik/traefik/releases/tag/v3.7.3PatchRelease Notes
• https://github.com/traefik/traefik/security/advisories/GHSA-9cr8-q42q-g8m7ExploitMitigationPatch
• https://access.redhat.com/security/cve/CVE-2026-53622
• https://bugzilla.redhat.com/show_bug.cgi?id=2491924
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53622.json