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

Source

https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-46339.yaml

Associated Vulnerability

Title: 9Router: Unauthenticated Remote Code Execution via unprotected MCP custom plugin routes (CVE-2026-46339)
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.

Description

9Router <= 0.4.36 middleware only guards 8 explicitly listed routes, leaving /api/cli-tools/* and /api/mcp/* entirely unauthenticated. An attacker can POST to /api/cli-tools/cowork-settings to register a custom MCP plugin with attacker-controlled command and args stored verbatim into globalThis, then GET /api/mcp/{name}/sse to trigger spawn() with the stored command resulting in unauthenticated remote code execution.

File Snapshot

Remarks

1. It is advised to access via the original source first.

2. Local POC snapshots are reserved for subscribers — if the original source is unavailable, the local mirror is part of the paid plan.

View subscription plans →