Medium severity · published Sep 14, 2026
CVE-2026-53718
Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass
6.4
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
GA
gateway · envoyproxy
< 1.7.4; >= 1.8.0-rc.0, < 1.8.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53718
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53718
github.com
https://github.com/envoyproxy/gateway/commit/5a78db82b7cf4fc5bebbeda2c50952892038a464
github.com
https://github.com/envoyproxy/gateway/commit/96e2b750868a459ace4b8b68e6a6e4fb0152b9b7
github.com
https://github.com/envoyproxy/gateway/commit/b4737180c7e597490c6363075c565fa8cf24eead
github.com
https://github.com/envoyproxy/gateway/pull/9171
github.com
https://github.com/envoyproxy/gateway/pull/9172
github.com
https://github.com/envoyproxy/gateway/pull/9173
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