# CVE-2026-46339: 9Router: Unauthenticated Remote Code Execution via unprotected MCP custom plugin routes

> Unauthenticated attackers can execute arbitrary commands via unprotected MCP plugin routes in 9Router, requiring an upgrade to secure the application.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** GHSA-fhh6-4qxv-rpqj

## What is CVE-2026-46339?

CVE-2026-46339 is a critical command injection vulnerability in decolua 9router, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

9Router is an AI router & token saver. From 0.4.30 until 0.4.37, 9Router's src/proxy.js middleware did not protect /api/cli-tools/* and /api/mcp/*, allowing unauthenticated registration of customPlugins through src/app/api/cli-tools/cowork-settings/route.js and command execution through the MCP bridge. This vulnerability is fixed in 0.4.37.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command), CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-46339?

2 open source packages ship an affected version, including 9router.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `9router` | npm | From 0.4.30 | 0.4.37 |
| `9router` | npm | From 0.4.30 | 0.4.37 |

## How do I fix CVE-2026-46339?

Upgrade 9router to 0.4.37 or later.

## Is CVE-2026-46339 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46339 exists.

Public exploit code:

- A specialized Python framework that executes unauthenticated remote code execution via the 9Router Model Context Protocol (MCP) bridge by deploying a 33-layer temporal phase cascade, Riemann-Hadamard dispersion, and an 11 ns wedge filter to bypass traditional proxy and process-monitoring defenses. (github_poc): https://github.com/SimoesCTT/CTT-Enhanced-CVE-2026-46339-Exploit-Engine
- 9Router <= 0.4.36 - Unauthenticated RCE (nuclei): http/cves/2026/CVE-2026-46339.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46339 and fix it if it is affected.

What it is: CVE-2026-46339 is a critical command injection vulnerability in decolua 9router, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46339 exists.

Affected packages and fixed versions:
- 9router (npm): affected from 0.4.30; fixed in 0.4.37
- 9router (npm): affected from 0.4.30; fixed in 0.4.37

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-2026-46339/ (Markdown: https://insights.sbomify.com/CVE-2026-46339/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46339
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46339
- OSV: https://osv.dev/vulnerability/CVE-2026-46339

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46339/
Summaries are generated and may contain mistakes; the official description above is the record.