Bug 2533373 (CVE-2026-53718)

Summary: CVE-2026-53718 github.com/envoyproxy/gateway: Envoy Gateway: Cross-namespace authorization bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Envoy Gateway. An attacker could exploit a vulnerability in how HTTPRoute handles custom backend references. This allows a route-owning namespace to access and utilize resources in another namespace without proper authorization, bypassing the intended Gateway API cross-namespace authorization model. This could lead to unauthorized resource usage and a violation of security boundaries within a Kubernetes environment.
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Description OSIDB Bzimport 2026-09-14 20:31:23 UTC 
Envoy Gateway is an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway. Prior to 1.7.4 and 1.8.1, an HTTPRoute can use an extension-managed custom backendRef to reference a backend resource in another namespace without a matching Gateway API ReferenceGrant in the target namespace. The custom-backend branch in internal/gatewayapi/route.go omits validateBackendNamespace, allowing the route-owning namespace to bind to and use the resource without the backend namespace owner's consent and violating the Gateway API cross-namespace authorization model. This issue is fixed in versions 1.7.4 and 1.8.1.