What’s Vulnerable › Vulnerabilities

CVE-2026-53718: Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-14 · updated 2026-09-25
• Weakness: CWE-862

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: before 1.7.4; from 1.8.0-rc.0, < 1.8.1

References

• 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/pull/9171
• https://github.com/envoyproxy/gateway/pull/9172
• https://github.com/envoyproxy/gateway/pull/9173
• https://github.com/envoyproxy/gateway/releases/tag/v1.7.4
• https://github.com/envoyproxy/gateway/releases/tag/v1.8.1
• https://github.com/envoyproxy/gateway/security/advisories/GHSA-fcrp-7gc2-93g7

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