high CVSS 7.1 EPSS 0.37%

CVE-2026-54761·Traefik vulnerability

Traefik is an HTTP reverse proxy and load balancer. Prior to 3.6.21 and 3.7.5, there is a high severity vulnerability in Traefik's Kubernetes Gateway provider affecting the crossProviderNamespaces allowlist. For HTTPRoute rules that declare multiple (WRR) backendRefs, Traefik evaluates the allowlist against the target backendRef.namespace instead of the route's own namespace. As a result, an HTTPRoute created in a namespace that is not allow-listed can reference a cross-provider TraefikService such as api@internal, dashboard@internal or rest@internal by pointing backendRef.namespace at an allow-listed namespace covered by a Gateway API ReferenceGrant, exposing internal Traefik services on the data plane. Exploitation requires the ability to create an accepted HTTPRoute and a matching ReferenceGrant from an allow-listed namespace; it does not require any change to Traefik static configuration, RBAC, or the deployment itself. This vulnerability is fixed in 3.6.21 and 3.7.5.

Severity
high
Software
Traefik
Fixed in
3.7.5
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 0.37% — higher than 28% 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-2026-54761 scores 7.1 on CVSS, so a successful attack would be serious — but at 0.37%, 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: 3.7.5

Fixed in: 3.7.5

How to fix this CVE

Upgrade Traefik to version 3.7.5 or later to patch a namespace validation bypass in the Kubernetes Gateway provider. This vulnerability allows attackers with HTTPRoute creation permissions to expose internal Traefik services by exploiting improper allowlist validation when using multiple backend references. Update immediately if you use Kubernetes Gateway API with cross-provider namespace restrictions.

sudo dnf update traefik

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET requests to /_internal/, /api/dashboard, or /rest endpoints originating from HTTPRoutes in non-allowlisted namespaces; access logs showing 'api@internal', 'dashboard@internal', or 'rest@internal' in backendRef fields within HTTPRoute objects

How to check if you are affected

  1. Check installed Traefik version: traefik version or grep -i version /path/to/traefik/config.yaml
  2. Verify if Kubernetes Gateway API provider is enabled: grep -i 'kubernetesgateway\|providers.kubernetesgateway' /path/to/traefik/static-config.yaml
  3. Check for HTTPRoutes with multiple backendRefs: kubectl get httproutes -A -o yaml | grep -A 5 'backendRefs'
  4. Review audit logs for access to internal services (api@internal, dashboard@internal, rest@internal): kubectl logs -n traefik deployment/traefik | grep -i 'api@internal\|dashboard@internal\|rest@internal'

FAQ

What is CVE-2026-54761?

This vulnerability allows authenticated users to bypass Kubernetes namespace restrictions in Traefik's Gateway API implementation by crafting HTTPRoutes with multiple backend references, potentially exposing internal management services like the dashboard and REST API.

Is CVE-2026-54761 being actively exploited?

No, this vulnerability is not listed as actively exploited in CISA's Known Exploited Vulnerabilities (KEV) catalog, and no public exploits are currently available.

What versions of Traefik are affected by CVE-2026-54761?

Traefik versions 3.7.0 through 3.7.4 are affected. Version 3.6.x before 3.6.21 is also vulnerable. The issue is resolved in 3.7.5 and 3.6.21.

How do I check if my server is vulnerable to CVE-2026-54761?

Run 'traefik version' and confirm the version is 3.7.0–3.7.4 or 3.6.0–3.6.20. Then verify Kubernetes Gateway API is enabled with 'grep -i kubernetesgateway /etc/traefik/traefik.yml' or check your Helm/deployment configuration.

Does Defensia detect CVE-2026-54761?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-54761 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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