AG-003: Unauthenticated MCP Server

What this rule means

MCP server accepts connections without authentication.

Why it matters

NSA guidance (May 2026) warns 200,000+ MCP instances are vulnerable.

How to fix it

Enable OAuth 2.1 authentication on MCP servers.

Detect it

pip install lucin
lucin scan .                  # all rules
lucin explain AG-003          # this rule, in your terminal

Findings carry a file:line and, where the rule supports it, a witness path showing the flow that triggered it. Precision and recall for the whole rule set, with the commands that regenerate them, are on the benchmarks page — and the gaps are on limits.

← All detection rules