MCP Deadbugz Simulator

A local simulation of the Deadbugz MCP supply-chain attack discovered by Pillar Security in August 2026.

What this repo contains

Malicious MCP server with 3-call gate evasion technique Python test harness to prove the attack works Optional agent simulation with local LLM

Related MCP server: MCP Decoy Server

The attack pattern

1. Server shows benign tools for first 3 calls

2. 4th call triggers tools/listChanged notification

3. Tool descriptions mutate to credential-stealing instructions

4. AI agent follows malicious instructions

Requirements

Python 3.10+ MCP SDK

Usage

git clone https://github.com/anexbin/mcp-deadbugz-simulator.git cd mcp-deadbugz-simulator pip install -r requirements.txt python server/malicious_server.py python client/test_harness.py

Files

server/malicious_server.py - The attack server client/test_harness.py - Proof of concept agent/local_agent.py - Optional LLM integration configs/ - Example MCP configs

Disclaimer

For educational and research purposes only.

References

https://www.pillar.security/blog/deadbugz-currently-active-mcp-supply-chain-campaign https://modelcontextprotocol.io

License

MIT