CVE-2026-53718
Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass
Description
### Impact Envoy Gateway accepts extension-managed custom backendRefs from an HTTPRoute to a backend resource in another namespace without requiring a matching Gateway API ReferenceGrant in the target namespace. This breaks the Gateway API cross-namespace consent model: the namespace that owns the referenced backend resource does not need to opt in with a ReferenceGrant before another namespace’s HTTPRoute can use that resource. ### Patches [1.7.4](https://github.com/envoyproxy/gateway/releases/tag/v1.7.4) [1.8.1](https://github.com/envoyproxy/gateway/releases/tag/v1.8.1)
How to fix CVE-2026-53718
To remediate CVE-2026-53718, upgrade the affected package to a fixed version below.
- —upgrade to 1.8.1 or later
Is CVE-2026-53718 being exploited?
No exploitation signal available. Neither CISA KEV nor a current EPSS score has been published for CVE-2026-53718.
Affected packages (1)
- >= 1.8.0-rc.0, < 1.8.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.4 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L |