CVE-2026-53718: Envoyproxy Gateway

Medium severity, CVSS 6.4. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Envoyproxy Gateway: before 1.7.4 (fixed in 1.7.4); from 1.8.0-rc.0, before 1.8.1 (fixed in 1.8.1)

Published 2026-09-14. Last modified 2026-09-25.