EUVD-2026-47645
GHSA-6mxq-jr92-3h2r
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Cross-namespace ReferenceGrant is non-default (AC:H); PR:L for route author; scope changes to downstream services (S:C) with high header-injection C/I impact; no availability effect.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
2DescriptionCVE.org
Traefik versions 3.7.0 through 3.7.6 contain a namespace confusion vulnerability in the Kubernetes Gateway API provider. When resolving HTTPRoute.spec.rules[].backendRefs[].filters[].extensionRef, Traefik used the backend Service namespace instead of the HTTPRoute namespace. A low-privileged route author holding a ReferenceGrant for a cross-namespace Service could therefore bind a Traefik Middleware from the backend namespace without a separate grant for that middleware, potentially injecting trusted reverse-proxy identity headers into downstream requests. The issue is fixed in version 3.7.7.
AnalysisAI
Namespace confusion in Traefik's Kubernetes Gateway API provider (versions 3.7.0-3.7.6) enables a low-privileged route author to attach unauthorized Traefik Middleware objects from foreign namespaces by exploiting incorrect namespace resolution in HTTPRoute extensionRef handling. An attacker holding an existing ReferenceGrant for a cross-namespace Service can leverage the flaw to inject trusted reverse-proxy identity headers into downstream requests - without a separate ReferenceGrant authorizing the Middleware - potentially bypassing authorization controls in backend services that trust those headers. No public exploit or CISA KEV listing has been identified at time of analysis; vendor-released fix is version 3.7.7.
Technical ContextAI
Traefik is a cloud-native reverse proxy and load balancer commonly deployed as a Kubernetes Ingress or Gateway API controller. The Kubernetes Gateway API's HTTPRoute resource supports extensionRef filters that allow attachment of provider-specific extensions such as Traefik Middleware objects. Cross-namespace resource references in the Gateway API model are access-controlled through ReferenceGrant objects, which must explicitly authorize each cross-namespace binding independently. CWE-863 (Incorrect Authorization) captures the root cause: Traefik's resolution logic for HTTPRoute.spec.rules[].backendRefs[].filters[].extensionRef incorrectly derived the lookup namespace from the referenced backend Service's namespace rather than from the HTTPRoute's own namespace. This caused an existing ReferenceGrant for a cross-namespace Service to be erroneously treated as implicitly authorizing Middleware references in that same Service namespace - collapsing two distinct authorization grants into one, violating the Gateway API security model. The affected CPE is cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* covering versions 3.7.0 through 3.7.6.
RemediationAI
The primary remediation is to upgrade Traefik to version 3.7.7 or later, which corrects the namespace resolution logic so that extensionRef is evaluated against the HTTPRoute's own namespace rather than the backend Service's namespace. The vendor advisory is at https://github.com/traefik/traefik/security/advisories/GHSA-qq9q-x9w4-chhj and the fix commit is at https://github.com/traefik/traefik/commit/26c96a3935cafb473f4a5bae1886560d9aa4e4f0. Where immediate upgrade is not feasible, administrators should audit all ReferenceGrant objects in the cluster and revoke any cross-namespace grants that are not explicitly required - reducing the pool of namespaces an attacker can pivot into. Disabling the Kubernetes Gateway API provider entirely (reverting to IngressRoute resources) removes the vulnerable code path, though this requires migration of routing configuration and is disruptive. Restricting Traefik's RBAC so it cannot read HTTPRoute or Middleware resources from untrusted namespaces limits exploitation but may break legitimate cross-namespace routing. Note that restricting ReferenceGrant usage has the side effect of preventing intentional cross-namespace Service references that may be required by existing workloads.
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