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Vulnerability · Published Sep 14, 2026 · Assigned by GitHub_M

CVE-2026-53718Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass

Medium 6.4

In plain English

A medium-severity missing authorization in gateway from envoyproxy. 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 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.4Medium
Exploit odds (30 days)0.4%top 64.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/envoyproxy/gateway1.8.1GHSA-fcrp-7gc2-93g7
Gogithub.com/envoyproxy/gateway1.7.4GHSA-fcrp-7gc2-93g7
Gogithub.com/envoyproxy/gateway1.7.4, 1.8.1GO-2026-6007

Affected products (as reported)

VendorProductVersions
envoyproxy gateway < 1.7.4>= 1.8.0-rc.0, < 1.8.1

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L

References