MCP-HARDENED

A deliberately small MCP server built to demonstrate security hardening against the OWASP MCP Top 10, with a test suite that proves the defenses hold.

Status

In progress. Day 1 of 7 — scaffold and transport smoke test only.

Related MCP server: Vulnerable MCP Server

Warning

Early commits contain intentionally vulnerable implementations. The build order is deliberate: write the naive version, write attack tests that prove the vulnerability is reachable, then harden until the tests pass. A security test that has never failed is not a test.

Do not use any commit from this repo as a reference implementation until the hardening commits land.

Planned scope

Three read-only tools, each hosting one vulnerability class:

Plus audit logging of every tool call and its arguments.

Explicitly out of scope

• Prompt injection — unsolved industry-wide, not attempting

• Tool poisoning — a consuming-side threat; a server cannot prevent a client from connecting to a poisoned server

• Multi-user authentication, rate limiting

Stack

Python 3.12 · FastMCP 3.3.1 · pytest · stdio transport