{"id":"CVE-2026-53718","state":"PUBLISHED","title":"Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass","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.","publishedAt":"2026-09-14T20:12:12.224Z","updatedAt":"2026-09-15T13:55:25.432Z","severity":{"score":6.4,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["envoyproxy gateway"],"affected":[{"vendor":"envoyproxy","product":"gateway","versions":[{"version":"< 1.7.4","status":"affected"},{"version":">= 1.8.0-rc.0, < 1.8.1","status":"affected"}]}],"references":["https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7","https://github.com/envoyproxy/gateway/pull/9171","https://github.com/envoyproxy/gateway/pull/9172","https://github.com/envoyproxy/gateway/pull/9173","https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464","https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7","https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead","https://github.com/envoyproxy/gateway/releases/tag/v1.7.4","https://github.com/envoyproxy/gateway/releases/tag/v1.8.1"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53718.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53718","state":"PUBLISHED","datePublished":"2026-09-14T20:12:12.224Z","dateUpdated":"2026-09-15T13:55:25.432Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-10T16:43:31.241Z"},"containers":{"cna":{"title":"Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass","descriptions":[{"lang":"en","value":"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":[{"vendor":"envoyproxy","product":"gateway","versions":[{"version":"< 1.7.4","status":"affected"},{"version":">= 1.8.0-rc.0, < 1.8.1","status":"affected"}]}],"references":[{"url":"https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7","name":"https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/envoyproxy/gateway/pull/9171","name":"https://github.com/envoyproxy/gateway/pull/9171","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/pull/9172","name":"https://github.com/envoyproxy/gateway/pull/9172","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/pull/9173","name":"https://github.com/envoyproxy/gateway/pull/9173","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464","name":"https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7","name":"https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead","name":"https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/releases/tag/v1.7.4","name":"https://github.com/envoyproxy/gateway/releases/tag/v1.7.4","tags":["x_refsource_MISC"]},{"url":"https://github.com/envoyproxy/gateway/releases/tag/v1.8.1","name":"https://github.com/envoyproxy/gateway/releases/tag/v1.8.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":6.4,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","description":"CWE-862: Missing Authorization","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-14T20:12:12.224Z"},"source":{"advisory":"GHSA-fcrp-7gc2-93g7","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-15T13:25:21.526527Z","id":"CVE-2026-53718","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-15T13:55:25.432Z"}}]}}}