Traefik: Kubernetes Gateway crossProviderNamespaces bypass allows HTTPRoute outside the allowlist to expose internal Traefik services

Summary

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.

Timeline

1. Jun 23, 2026, 7:15 PM UTCCVE published
2. Jun 25, 2026, 12:45 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jun 25, 2026, 12:45 PM UTCRecord last updated

Affected versions

• traefik traefik

  fixed in 3.6.21; From 3.7.0-ea.1 · fixed in 3.7.5

• github.com/traefik/traefik/v3Go

  fixed in 3.6.21

• github.com/traefik/traefik/v2Go

  through 2.11.50

• github.com/traefik/traefikGo

  through 1.7.34

• github.com/traefik/traefik/v3Go

  From 3.7.0-ea.1 · fixed in 3.7.5

• github.com/traefik/traefikGo

  All versions

• github.com/traefik/traefik/v2Go

  All versions

• github.com/traefik/traefik/v3Go

  fixed in 3.6.21; From 3.7.0-ea.1 · fixed in 3.7.5

References 4