# CVE-2026-18676: Kong Mesh: default control plane config leaks the admin token cross-origin via a CORS wildcard and localhost admin

> Default Kong Mesh configuration exposes admin tokens and keys to cross-origin requests, allowing attackers to steal credentials and escalate privileges.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 12 Aug 2026
- **Updated:** 13 Aug 2026
- **Also known as:** GHSA-x23j-4pcq-m26j

## What is CVE-2026-18676?

CVE-2026-18676 is a medium-severity vulnerability in Kong Mesh, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The default kuma-cp configuration in Kong Mesh reveals the admin bootstrap token and signing keys to any webpage the operator visits while the control plane is reachable from their browser. Due to a CORS misconfiguration a cross-origin fetch() from a malicious page returns the admin JWT and signing material.

Weakness: CWE-942 (Permissive Cross-domain Security Policy with Untrusted Domains), CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-18676?


## How do I fix CVE-2026-18676?

Apply the vendor's patch.

## Is CVE-2026-18676 being exploited?

There is no known exploitation of CVE-2026-18676 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18676 and fix it if it is affected.

What it is: CVE-2026-18676 is a medium-severity vulnerability in Kong Mesh, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-18676 in the wild and no public exploit code.

Affected product: Kong Mesh. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-18676/ (Markdown: https://insights.sbomify.com/CVE-2026-18676/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18676
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18676
- OSV: https://osv.dev/vulnerability/CVE-2026-18676

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18676/
Summaries are generated and may contain mistakes; the official description above is the record.