Bug 2491920 (CVE-2026-54761)

Summary: CVE-2026-54761 traefik: Traefik: Internal service exposure due to crossProviderNamespaces allowlist misconfiguration
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik, an HTTP reverse proxy and load balancer. This vulnerability exists in the Kubernetes Gateway provider's `crossProviderNamespaces` allowlist. A remote attacker with the ability to create an accepted HTTPRoute and a matching ReferenceGrant can exploit this by misconfiguring the `backendRef.namespace` to bypass the allowlist. This allows the attacker to expose internal Traefik services, such as the API or dashboard, on the data plane, leading to information disclosure.
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Description OSIDB Bzimport 2026-06-23 20:01:38 UTC 
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.