Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.4 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L

EPSS

• CVE-2026-53718: 0.41% estimated exploitation activity in the next 30 days; percentile 35.62 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 1.8.1

Published by the source

16 Jul 2026, 19:14 UTC

Last modified by the source

16 Jul 2026, 19:14 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fcrp-7gc2-93g7

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# Patch Next advisory brief: CVE-2026-53718

Advisory: Envoy Gateway custom backendRef cross-namespace ReferenceGrant bypass
IDs: CVE-2026-53718, GHSA-fcrp-7gc2-93g7
Record: https://patchnext.com/advisories/cve-2026-53718 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/envoyproxy/gateway 1.8.1, 1.7.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/envoyproxy/gateway: affected >= 1.8.0-rc.0, < 1.8.1; < 1.7.4; fixed in 1.8.1, 1.7.4

## Suggested inspection (read-only)
- Go github.com/envoyproxy/gateway: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/envoyproxy/gateway.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fcrp-7gc2-93g7 (GitHub-reviewed advisory GHSA-fcrp-7gc2-93g7 lists affected ranges: Go github.com/envoyproxy/gateway >=1.8.0-rc.0 =0 <1.7.4)

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