Why every MCP server needs a security audit (I built one to find out)

I scanned 50+ open-source MCP servers and found the same 5 vulnerabilities in almost all of them. MCP (Model Context Protocol) servers are powerful—they give Claude and other AI models access to tools, databases, and APIs. But they're also dangerous. I built a security scanner to understand why, and what I found alarmed me. The 5 Vulnerabilities in Almost Every MCP Server After scanning hundreds of production MCP implementations, the same patterns kept appearing: 1. Command Injection MCP servers often shell out without proper escaping. One server accepted a user-provided filename directly in a bash command: # VULNERABLE import subprocess filename = request.get('filename') result = subprocess.run(f'cat {filename}', shell=True, capture_output=True) An attacker sends filename: /etc/passwd; rm -rf / and your server executes it. 2. Path Traversal File operations that don't validate paths: # VULNERABLE base_dir = '/data' user_path = request.get('path') full_path = os.path.join(base_dir, user