# CVE-2026-53718

## Summary

- **CVE ID:** CVE-2026-53718
- **Severity:** MEDIUM
- **CVSS Score:** 6.4 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L)
- **CWE:** CWE-862
- **Published:** Sep 14, 2026
- **Last Modified:** Sep 15, 2026

## 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 Products

- envoyproxy — gateway (< 1.7.4)
- envoyproxy — gateway (>= 1.8.0-rc.0, < 1.8.1)

## References

- [CNA](https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7)
- [CNA](https://github.com/envoyproxy/gateway/pull/9171)
- [CNA](https://github.com/envoyproxy/gateway/pull/9172)
- [CNA](https://github.com/envoyproxy/gateway/pull/9173)
- [CNA](https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464)
- [CNA](https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7)
- [CNA](https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead)
- [CNA](https://github.com/envoyproxy/gateway/releases/tag/v1.7.4)
- [CNA](https://github.com/envoyproxy/gateway/releases/tag/v1.8.1)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.33%
- **EPSS Percentile:** 25.8

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._