critical CVSS 9.8 EPSS 0.44%

CVE-2026-85596·Traefik vulnerability

Traefik versions >= v3.7.0 and <= v3.7.10 contain an authentication bypass in the Kubernetes Ingress NGINX provider. The TLS option generated for an Ingress carrying the nginx.ingress.kubernetes.io/auth-tls-secret annotation was named after the Ingress namespace and name. As a result, two Ingress objects sharing the same host, the same client CA secret, and the same client-authentication mode produced two distinct TLS option names for that host. Traefik treats this as a TLS options conflict and falls back to the entry point's default TLS configuration, which does not request a client certificate, so a route configured with nginx.ingress.kubernetes.io/auth-tls-verify-client: "on" becomes reachable without a client certificate. Only the v3.7 line is affected; the issue is fixed in v3.7.11.

Severity
critical
Software
Traefik
Fixed in
3.7.11
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.44% — higher than 36% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-85596 scores 9.8 on CVSS, so a successful attack would be serious — but at 0.44%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 3.7.0

Until: 3.7.11

Fixed in: 3.7.11

How to fix this CVE

Upgrade Traefik to version 3.7.11 or later immediately to resolve the TLS option naming conflict that allows client certificate authentication to be bypassed. Organizations running Traefik 3.7.0 through 3.7.10 with Kubernetes Ingress NGINX providers should prioritize this update, especially if they rely on client certificate validation (auth-tls-verify-client: on) for securing routes.

sudo dnf update traefik

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check installed Traefik version with 'traefik version' or 'docker inspect <traefik-container> | grep -i version' if containerized
  2. Step 2: If running on Kubernetes, verify Ingress objects with 'kubectl get ingress -A' and check for annotations containing 'nginx.ingress.kubernetes.io/auth-tls-secret' and 'nginx.ingress.kubernetes.io/auth-tls-verify-client: on'
  3. Step 3: Search Traefik logs for TLS option conflicts: 'grep -i "tls.*conflict\|tls.*fallback" /var/log/traefik.log' or check container logs with 'docker logs <traefik-container> | grep -i tls'
  4. Step 4: After upgrade, restart Traefik and verify version: 'traefik version | grep -E "Version|v3\.7\.1[1-9]"' confirming version >= 3.7.11

FAQ

What is CVE-2026-85596?

This vulnerability affects Traefik's Kubernetes Ingress NGINX provider where duplicate Ingress objects sharing the same host and client CA secret cause conflicting TLS option names, forcing Traefik to fall back to unauthenticated TLS defaults and allowing unauthenticated access to routes that should require client certificates.

Is CVE-2026-85596 being actively exploited?

No, there are currently no public exploits or active exploitation reports in the CISA Known Exploited Vulnerabilities catalog, though the critical CVSS score (9.8) warrants immediate patching.

What versions of Traefik are affected by CVE-2026-85596?

Traefik versions 3.7.0 through 3.7.10 are vulnerable; the v3.2 line and earlier are unaffected. The fix is available in v3.7.11 and later.

How do I check if my server is vulnerable to CVE-2026-85596?

Run 'traefik version' and verify the output shows v3.7.0–v3.7.10; also check Kubernetes Ingress annotations with 'kubectl get ingress -A -o json | grep -i auth-tls-secret' to identify affected configurations.

Does Defensia detect CVE-2026-85596?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-85596 will appear in your dashboard with remediation steps.

Related Traefik CVEs

CVE-2026-53622CVSS 10Traefik 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.
CVE-2026-48491CVSS 10Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik's domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3.
CVE-2026-48020CVSS 10Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.48, 3.6.19, and 3.7.3, there is a high severity vulnerability in Traefik's StripPrefix middleware that allows an unauthenticated attacker to bypass route-level authentication and authorization. When a public router matches on a PathPrefix rule and applies the StripPrefix middleware, a request path containing .. or its percent-encoded form %2e%2e can match the public route at routing time and then, after the prefix is stripped and the path is normalized, resolve to a path served by a separate, authenticated router. As a result, an attacker can reach protected backend paths — such as admin or internal configuration endpoints — without satisfying the authentication middleware attached to the protected router. This vulnerability is fixed in 2.11.48, 3.6.19, and 3.7.3.
CVE-2026-54763CVSS 10Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
CVE-2026-44774CVSS 9.9Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.46, 3.6.17, and 3.7.1, Traefik's Kubernetes Gateway API provider allows a tenant with HTTPRoute creation permissions to expose the REST provider handler, bypassing the providers.rest.insecure=false setting. The Gateway provider accepts any TraefikService backend reference whose name ends with @internal, making it possible to route traffic to rest@internal in addition to the intended api@internal. In shared Gateway deployments where the REST provider is enabled, this allows a low-privileged actor to gain live dynamic configuration write access to Traefik, enabling unauthorized reconfiguration of routers and services. This vulnerability is fixed in 2.11.46, 3.6.17, and 3.7.1.

References

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