high CVSS 8.5 EPSS 0.35%

CVE-2026-54765·Traefik vulnerability

Traefik is an open source HTTP reverse proxy and load balancer. From v3.7.0 prior to v3.7.6, Traefik's Kubernetes Gateway API provider may resolve two accepted HTTPRoutes that target the same backend Service:port but configure different backendRef filters to the same child service and apply only one route's filter set to all requests reaching that backend. In Gateway deployments where backendRef filters set security-sensitive headers, such as tenant identity, authorization context, or values the backend trusts, an attacker who can create an accepted HTTPRoute sharing the same backend Service:port may cause their route's filter context to be applied to another route's requests, potentially crossing namespace boundaries when a ReferenceGrant permits cross-namespace targeting. This issue is fixed in version v3.7.6.

Severity
high
Software
Traefik
Fixed in
3.7.6
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 0.35% — higher than 26% 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-2026-54765 scores 8.5 on CVSS, so a successful attack would be serious — but at 0.35%, 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: 3.7.6

Fixed in: 3.7.6

How to fix this CVE

Upgrade Traefik to version 3.7.6 or later to resolve a critical filter configuration bypass in the Kubernetes Gateway API provider. This vulnerability allows attackers with HTTPRoute creation privileges to inject their security filters into unrelated routes sharing the same backend service, potentially exposing tenant isolation and authorization contexts. Immediately patch all Traefik instances running versions 3.7.0 through 3.7.5 in production Gateway environments.

sudo dnf update traefik

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your installed Traefik version by running: traefik version or docker inspect <traefik-container-id> | grep -i version
  2. Step 2: Query your Kubernetes cluster for all HTTPRoute resources across namespaces using: kubectl get httproutes -A and examine backendRef configurations for duplicate Service:port targets with different filter sets
  3. Step 3: Review Traefik logs for filter mismatch patterns by searching: grep -i 'filter\|backendref' /var/log/traefik/traefik.log and correlate with timestamps of HTTPRoute creation events
  4. Step 4: Verify the patch by confirming traefik version returns v3.7.6 or later, and restart Traefik to apply changes: sudo systemctl restart traefik or kubectl rollout restart deployment/traefik -n <namespace>

FAQ

What is CVE-2026-54765?

CVE-2026-54765 is a filter configuration bypass in Traefik's Kubernetes Gateway API implementation where multiple HTTPRoutes targeting the same backend Service:port can incorrectly share filter contexts, allowing an attacker to apply their security-sensitive filters (like authorization headers or tenant identity) to other routes' traffic.

Is CVE-2026-54765 being actively exploited?

No, this vulnerability is not currently listed on the CISA KEV catalog and has no confirmed public exploits, but it requires low privileges (HTTPRoute creation capability) and could be exploited opportunistically in shared Kubernetes Gateway environments.

What versions of Traefik are affected by CVE-2026-54765?

Traefik versions 3.7.0 through 3.7.5 are vulnerable; version 3.7.6 and later contain the fix.

How do I check if my server is vulnerable to CVE-2026-54765?

Run traefik version and confirm the output shows v3.7.0 through v3.7.5; also check if you're using the Kubernetes Gateway API provider by searching your Traefik configuration for 'kubernetesgateway' or 'gateway' provider declarations.

Does Defensia detect CVE-2026-54765?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-54765 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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