Toxy Insecure MCP Lab

⚠️ Read this first

Related MCP server: Insecure MCP Demo

Overview

Modern AI agents call external MCP tools the same way apps call APIs. When those tools skip authentication, trust user input, or run with too much power, attackers inherit that access.

Toxy Insecure MCP Lab models those failures in a single Python service you can drive from any MCP client, curl, or the MCP Inspector.

flowchart LR
    A[MCP Client] -->|STDIO / SSE / HTTP| B[Toxy Lab]
    B --> C[Open Tools]
    B --> D[Weak Auth Tools]
    B --> E[File Tools]
    B --> F[SSRF Tools]
    B --> G[SQLi Tools]
    C --> H[(Mock Data)]
    D --> H
    E --> I[Container FS]
    F --> J[Outbound HTTP]
    G --> K[(SQLite DB)]

Lab snapshot

Requirements

• Python 3.11+ or Docker with Compose v2

• An MCP client, MCP Inspector, or curl

• An isolated network (VM, WSL, or local machine — not a shared server)

Installation paths

git clone https://github.com/toxicaj/vuln_mcp_server.git
cd vuln_mcp_server
docker compose up --build

The service listens on port 8000. Connect your client to http://localhost:8000/mcp.

git clone https://github.com/toxicaj/vuln_mcp_server.git
cd vuln_mcp_server
python -m venv .venv
source .venv/bin/activate          # Windows: .venv\Scripts\activate
pip install -r requirements.txt

Pick a transport:

Note: Local HTTP/SSE runs need a writable database path. Example: DATABASE_PATH=/tmp/toxy_vulnerable_mcp.sqlite

Attack surface

Five independent modules. Each one teaches a different mistake teams make when shipping MCP integrations.

Module 01 — Identity not required

File: toxy_vulnerable_mcp/tools/unauth_tools.py

Try it

{ "name": "system_info", "arguments": {} }

Lesson: If a tool returns sensitive data without a session, every connected agent becomes an insider threat.

Module 02 — Password everyone knows

File: toxy_vulnerable_mcp/tools/auth_tools.py

Credentials are hardcoded: admin:admin

Try it (HTTP)

curl http://localhost:8000/mcp \
  -u admin:admin \
  -H 'Content-Type: application/json' \
  -H 'Mcp-Method: tools/call' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"get_sensitive_logs","arguments":{}}}'

Lesson: Default passwords turn a thin auth layer into theater.

Module 03 — Filesystem god mode

File: toxy_vulnerable_mcp/tools/file_tools.py

Writable mounts: /lab-data · /app/secrets · /data

Try it

{
  "name": "write_file",
  "arguments": {
    "path": "/lab-data/proof.txt",
    "content": "MCP tool wrote this with root privileges"
  }
}

Lesson: File tools without jails hand agents the keys to the kingdom.

Module 04 — Server-side fetching

File: toxy_vulnerable_mcp/tools/ssrf_tools.py

Try it

{ "name": "fetch_url", "arguments": { "url": "http://127.0.0.1:8000/mcp" } }

{ "name": "fetch_url", "arguments": { "url": "http://169.254.169.254/latest/meta-data/" } }

Lesson: Unrestricted egress lets callers scan localhost and cloud metadata from inside your network.

Module 05 — String-built SQL

File: toxy_vulnerable_mcp/tools/sqli_tools.py

Try it — auth bypass

{
  "name": "login_user",
  "arguments": { "username": "admin' --", "password": "x" }
}

Try it — UNION extraction

{
  "name": "get_order",
  "arguments": {
    "order_id": "1 UNION SELECT id, record_type, secret_value, 0, 'leak' FROM admin_records"
  }
}

Lesson: Concatenating user input into SQL is an open invitation to dump tables you never meant to expose.

HTTP cheat sheet

Three calls cover most manual testing:

1. Initialize

curl -i http://localhost:8000/mcp \
  -H 'Content-Type: application/json' \
  -H 'Mcp-Method: initialize' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"lab","version":"1.0"}}}'

2. List tools

curl http://localhost:8000/mcp \
  -H 'Content-Type: application/json' \
  -H 'Mcp-Method: tools/list' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}'

3. Call a tool

curl http://localhost:8000/mcp \
  -H 'Content-Type: application/json' \
  -H 'Mcp-Method: tools/call' \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"list_users","arguments":{}}}'

Directory map

vuln_mcp_server/
│
├─ docker-compose.yml      # One-command lab spin-up
├─ Dockerfile              # Root-user image (intentional)
├─ lab-data/               # Writable practice files
├─ secrets/                # Fake credentials for file-read labs
│
└─ toxy_vulnerable_mcp/
   ├─ server.py            # MCP entry + transport launcher
   ├─ http_app.py          # HTTP wrapper + Basic Auth middleware
   ├─ auth.py              # admin:admin validator
   ├─ database.py          # SQLite seed data
   ├─ data.py              # Mock notes, users, logs
   └─ tools/
      ├─ unauth_tools.py
      ├─ auth_tools.py
      ├─ file_tools.py
      ├─ ssrf_tools.py
      └─ sqli_tools.py

Logging & debugging

Everything runs at DEBUG by default. Watch for:

• Open * invocation — unauthenticated tool hits

• Basic Auth gate triggered — credential checks on protected tools

• Outbound request issued to — SSRF attempts

• Running unsafe SQL statement — full query text before execution

• read_file / write_file / list_directory — filesystem operations

docker compose logs -f

FAQ

Q: Can I rename the repo folder after cloning?
A: Yes. The folder name does not affect runtime behavior.

Q: Why does local setup fail on /data?
A: The default DB path targets the Docker layout. Set DATABASE_PATH=/tmp/toxy_vulnerable_mcp.sqlite when running natively.

Q: Do I need to wipe Docker volumes between runs?
A: Only if you changed the database filename or seed schema. docker compose down -v resets state.

Q: Are the employee names and API keys real?
A: No. All records are synthetic classroom material.

Hardening checklist

Use this after completing each module:

• Require authentication before any data-bearing tool executes

• Eliminate default credentials; integrate a real identity provider

• Remove open-ended file primitives or jail them to a single directory

• Block private IP ranges and metadata hosts on outbound fetches

• Parameterize every SQL statement; hash passwords at rest

• Run containers as non-root with read-only root filesystems

• Log security events without printing secrets or full queries in production

Legal & ethics

Deploy only on systems you own or have explicit written permission to test. The maintainer provides this software as-is for education — misuse against third parties is your responsibility.