{"id":"CVE-2026-53718","aliases":["BIT-envoy-gateway-2026-53718","GHSA-fcrp-7gc2-93g7","GO-2026-6007"],"url":"https://o3.security/vulnerability/CVE-2026-53718","summary":"Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass","details":"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.","published":"2026-09-14T20:12:12.224Z","modified":"2026-09-21T09:40:46.638359063Z","cvss":{"score":6.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L"},"epss":{"score":0.00327,"percentile":0.25758,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/envoyproxy/gateway","fixedVersion":"1.8.1"},{"ecosystem":"Go","name":"github.com/envoyproxy/gateway","fixedVersion":"1.7.4"}],"fix":{"url":"https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464","label":"envoyproxy/gateway@5a78db8"},"references":[{"type":"WEB","url":"https://github.com/envoyproxy/gateway/releases/tag/v1.7.4"},{"type":"WEB","url":"https://github.com/envoyproxy/gateway/releases/tag/v1.8.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53718.json"},{"type":"ADVISORY","url":"https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53718"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/pull/9171"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/pull/9172"},{"type":"FIX","url":"https://github.com/envoyproxy/gateway/pull/9173"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-21T09:40:46.638359063Z"}}