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TraefikApplication

CVE-2026-53622

CRITICAL · 10.0 CVSS v3.1 Published 2026-06-23
Fix available
A fix is available. Upgrade to 3.7.3 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Traefik versions prior to 3.7.3, HTTP/3 (QUIC) TLS handshake performs an exact, case-sensitive SNI lookup to select the TLS configuration. This fails to match wildcard host patterns (e.g., *.example.com) or case variants, causing fallback to the default TLS configuration that may not require client certificates. However, the HTTP routing layer still dispatches requests to backends protected by router-specific mTLS policies, allowing unauthenticated attackers to bypass mTLS authentication.

MitigationUpgrade Traefik to version 3.7.3 or later. Until upgraded, consider disabling HTTP/3 on entrypoints that enforce mTLS, or ensure UDP access to affected entrypoints is not reachable from untrusted networks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
TraefikApplication
Affected:< 3.7.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Traefik version
    Run `traefik version` or inspect the deployed binary/container image tag. Compare the version number to 3.7.3.
    Affected if The installed version is below 3.7.3.
  2. Identify HTTP/3 enabled entrypoints
    Review Traefik static configuration files (traefik.yml, traefik.toml, or --entrypoints flags) for `http3: true` entries under the entrypoints section.
    Affected if Any entrypoint has HTTP/3 enabled (http3: true).
  3. Check for mTLS-configured routers
    Review dynamic configuration for routers that define TLS with `clientAuth` settings (such as `clientAuth.type: RequestClientCert` or `RequireAndVerifyClientCert`).
    Affected if One or more routers enforce mTLS via clientAuth configuration.
  4. Identify default TLS configuration
    Inspect Traefik configuration for a TLS options definition without a specific `snis` or `domains` matcher, which serves as the default TLS fallback.
    Affected if A default TLS configuration exists that does not require client certificates, while mTLS routers use specific SNI/domain matching.

You are affected if running Traefik below version 3.7.3 with HTTP/3 enabled on entrypoints serving routers that enforce mTLS, where a fallback default TLS configuration lacks client certificate requirements.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.7.3 or later
Fixed in 3.7.3
Vendor patch github.com →
Interim mitigation

Upgrade Traefik to version 3.7.3 or later. Until upgraded, consider disabling HTTP/3 on entrypoints that enforce mTLS, or ensure UDP access to affected entrypoints is not reachable from untrusted networks.

Recommended fix High confidence

Traefik 3.7.3

  1. Identify all Traefik deployments running versions prior to 3.7.3
  2. Review configuration to determine if HTTP/3 (QUIC) is enabled on any entrypoints
  3. Identify routers using wildcard Host rules (e.g., Host(`*.example.com`)) or case-insensitive hostname matching
  4. Identify routers with TLSOptions enforcing client certificate authentication (clientAuth: { type: RequestClientCert | RequireAnyClientCert })
  5. Plan maintenance window for upgrade
  6. Upgrade Traefik to version 3.7.3 or later
  7. Verify HTTP/3 functionality continues to work after upgrade
  8. Confirm mTLS enforcement is properly applied to all affected routers by testing with and without client certificates
Caveat Review Traefik 3.7.x release notes for any breaking changes between current version and 3.7.3; minor version upgrades typically have low risk but HTTP/3 behavior changes should be tested

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Traefik Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53622 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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