Executive brief
Traefik is a popular open-source edge router and load balancer. A vulnerability in its Kubernetes integration allows a user who is restricted to one part of a cluster (a namespace) to bypass security boundaries and connect their own traffic rules to services belonging to other users. This could allow an attacker to expose internal services to the public internet or intercept traffic intended for another department or customer.
Technical details
A vulnerability exists in Traefik's Kubernetes CRD provider where the `allowCrossNamespace=false` setting (the default) is not honored for `TraefikService` backend references. While Traefik correctly enforces this boundary for middlewares and TLS options, the `nameAndService` resolver in `pkg/provider/kubernetes/crd/kubernetes_http.go` lacks the necessary validation logic for names containing the `@kubernetescrd` separator. An attacker with RBAC permissions to create an `IngressRoute` in their own namespace can reference a `TraefikService` in a different namespace, effectively binding their router to a victim's backend. This bypasses the intended multi-tenant isolation. Patches are available in versions 2.11.54, 3.6.25, and 3.7.10.
Affected products
- Traefik traefik/v2 <= 2.11.53
- Traefik traefik/v3 >= 3.0.0, <= 3.6.24; >= 3.7.0, <= 3.7.9
- Traefik traefik <= 1.7.34
Timeline
- 2026-08-03: advisory: GitHub Advisory published
- 2026-08-06: disclosed: Public disclosure of CVE-2026-71325