Vulnerability · Published Jun 23, 2026 · Assigned by GitHub_M
CVE-2026-54761Traefik: Kubernetes Gateway crossProviderNamespaces bypass allows HTTPRoute outside the allowlist to expose internal Traefik services
Medium 6.0
In plain English
A medium-severity improper access control in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/traefik/traefik | no fix listed | GO-2026-5083 |
| Go | github.com/traefik/traefik | no fix listed | GHSA-3g6v-2r68-prfc |
| Go | github.com/traefik/traefik/v2 | no fix listed | GO-2026-5083 |
| Go | github.com/traefik/traefik/v2 | no fix listed | GHSA-3g6v-2r68-prfc |
| Go | github.com/traefik/traefik/v3 | 3.7.5 | GHSA-3g6v-2r68-prfc |
| Go | github.com/traefik/traefik/v3 | 3.6.21 | GHSA-3g6v-2r68-prfc |
| Go | github.com/traefik/traefik/v3 | 3.6.21, 3.7.5 | GO-2026-5083 |
Affected products (as reported)
Weakness: CWE-284, CWE-863 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
References
- https://github.com/traefik/traefik/security/advisories/GHSA-3g6v-2r68-prfc x_refsource_CONFIRM
- https://github.com/traefik/traefik/releases/tag/v3.6.21 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.7.5 x_refsource_MISC