{"id":"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.","aliases":["BIT-envoy-gateway-2026-53718","GHSA-fcrp-7gc2-93g7","GO-2026-6007"],"modified":"2026-09-21T09:40:33.033237034Z","published":"2026-09-14T20:12:12.224Z","related":["openSUSE-SU-2026:21483-1"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-862"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53718.json"},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/envoyproxy/gateway","events":[{"introduced":"0"},{"introduced":"6d06f23e29068a7c8a5a9af5fc7a189807f031aa"},{"fixed":"062b176235b72d339fac340d23dd37679b36dca6"},{"fixed":"097ab899b9d041452d02f15d738514eda10ea21b"},{"fixed":"5a78db82b7cf4fc5bebbeda2c50952892038a464"},{"fixed":"96e2b750868a459ace4b8b68e6a6e4fb0152b9b7"},{"fixed":"b4737180c7e597490c6363075c565fa8cf24eead"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"1.7.4"},{"introduced":"1.8.0-rc.0"},{"fixed":"1.8.1"}]}}],"versions":["v1.8.0","v1.7.3","v1.8.0-rc.1","v1.9.0-rc.0","v1.7.2","v1.7.1","v1.8.0-rc.0","v1.7.0","v1.7.0-rc.2","v1.7.0-rc.1","v1.7.0-rc.0","v1.6.0-rc.0","latest","v0.5.0-rc.1","v0.2.0","v0.2.0-rc2","v0.2.0-rc1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-53718.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L"}]}