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

> Attackers can bypass cross-namespace authorization checks in Envoy Gateway to access backend resources in other namespaces without permission.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** BIT-envoy-gateway-2026-53718, CLEANSTART-2026-NI49374, CLEANSTART-2026-XJ72729, GHSA-fcrp-7gc2-93g7, GO-2026-6007, MINI-59pv-636w-8696, MINI-gwff-pfg3-fx7p, MINI-h9jr-48f9-xc26, MINI-qrgm-wrq4-c4f5

## What is CVE-2026-53718?

CVE-2026-53718 is a medium-severity missing authorization vulnerability in envoyproxy gateway, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-53718?

6 open source packages ship an affected version, including github.com/envoyproxy/gateway and envoy-gateway.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/envoyproxy/gateway` | Go | All versions | 1.7.4, 1.8.1 |
| `github.com/envoyproxy/gateway` | Go | All versions | 1.7.4 |
| `github.com/envoyproxy/gateway` | Go | All versions | 1.7.4 |
| `github.com/envoyproxy/gateway` | Go | From 1.8.0-rc.0 | 1.8.1 |
| `github.com/envoyproxy/gateway` | Go | From 1.8.0-rc.0 | 1.8.1 |
| `envoy-gateway` | Bitnami | All versions | 1.7.4, 1.8.1 |

## How do I fix CVE-2026-53718?

Upgrade github.com/envoyproxy/gateway to a fixed version for your release line: 1.7.4 or 1.8.1.

## Is CVE-2026-53718 being exploited?

There is no known exploitation of CVE-2026-53718 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53718 and fix it if it is affected.

What it is: CVE-2026-53718 is a medium-severity missing authorization vulnerability in envoyproxy gateway, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53718 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/envoyproxy/gateway (Go): affected all versions; fixed in 1.7.4, 1.8.1
- github.com/envoyproxy/gateway (Go): affected all versions; fixed in 1.7.4
- github.com/envoyproxy/gateway (Go): affected all versions; fixed in 1.7.4
- github.com/envoyproxy/gateway (Go): affected from 1.8.0-rc.0; fixed in 1.8.1
- github.com/envoyproxy/gateway (Go): affected from 1.8.0-rc.0; fixed in 1.8.1
- envoy-gateway (Bitnami): affected all versions; fixed in 1.7.4, 1.8.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53718/ (Markdown: https://insights.sbomify.com/CVE-2026-53718/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53718
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53718
- OSV: https://osv.dev/vulnerability/CVE-2026-53718

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53718/
Summaries are generated and may contain mistakes; the official description above is the record.