CTFd MCP server (user scope)

MCP server that lets a regular CTFd user list challenges, read details, start/stop dynamic docker instances, and submit flags.

Requirements

• Python 3.13 (managed by uv).
• Environment variables (choose one auth method):
• CTFD_URL (e.g. https://ctfd.example.com)
• CTFD_TOKEN (user token, not admin) or CTFD_SESSION (session cookie if tokens are disabled).
  • CTFD_CSRF_TOKEN (optional, only if the server/plugin requires CSRF for ctfd-owl).

You can store them in a .env file in the repo root:

CTFD_URL=https://ctfd.example.com/
CTFD_USERNAME=your_username
CTFD_PASSWORD=your_password
# or, if you prefer to use a token:
# CTFD_TOKEN=your_ctfd_api_token_here
# or, if tokens are disabled:
# CTFD_SESSION=your_session_token_here
# and, if the owl plugin enforces CSRF:
# CTFD_CSRF_TOKEN=your_csrf_token_here

Install

• From PyPI (recommended): uvx ctfd-mcp --help
• From source checkout (no install): uvx --from . ctfd-mcp --help

Run MCP server (stdio)

# installed from PyPI
uvx ctfd-mcp
# from local checkout
uvx --from . ctfd-mcp

Cursor and Claude MCP config example

{
  "mcpServers": {
    "ctfd-mcp": {
      "command": "uvx",
      "args": ["ctfd-mcp"],
      "env": {
        "CTFD_URL": "https://ctfd.example.com",
        "CTFD_TOKEN": "your_user_token"
      }
    }
  }
}

Codex MCP config example

[mcp_servers.ctfd-mcp]
command = "uvx"
args = ["ctfd-mcp"]

[mcp_servers.ctfd-mcp.env]
CTFD_URL = "https://ctfd.example.com"
CTFD_TOKEN = "your_user_token"

Exposed tools

• list_challenges(category?, only_unsolved?) — list visible challenges, optional category/unsolved filter.
• challenge_details(challenge_id) — description (HTML + description_text), metadata, attachment URLs, solved status.
• submit_flag(challenge_id, flag) — attempt a flag; returns status/message.
• start_container(challenge_id) — unified start; auto-detects dynamic_docker, ctfd-owl or k8s /api/v1/k8s.
• stop_container(container_id?, challenge_id?) — unified stop; whale can be stopped with just container_id, owl/k8s need challenge_id.

Attachments are returned as absolute URLs in files; the client/host can fetch them directly.

MCP resources

• resource://ctfd/challenges/{challenge_id} — markdown snapshot of a challenge (metadata, description, attachment URLs, connection info if present).

Error handling

• Missing env/config -> clear MCP error.
• 401/403 -> auth failed, check token or session cookie.
• 404 -> not found (or dynamic container API missing).
• 429 -> rate limited (Retry-After if present).
• Other HTTP/API errors -> surfaced as MCP errors with CTFd message/status.

Notes and troubleshooting

• Dynamic containers require the ctfd-whale (dynamic_docker) plugin on the target CTFd; otherwise /api/v1/containers returns 404.
• Owl challenges (dynamic_check_docker) use a different endpoint: /plugins/ctfd-owl/container?challenge_id=<id>. They usually require a session cookie, and some setups require a CSRF token; set CTFD_CSRF_TOKEN if needed.
• Some events expose Kubernetes-backed instances at /api/v1/k8s/{get,create,delete} with multipart form data; the client will try these when the challenge type includes k8s (or when a dynamic_docker endpoint is missing).
• If the server redirects you to /login (302) when using a token, switch to a browser session cookie: set CTFD_SESSION from the session cookie after logging in.
• The client now supports logging in with CTFD_USERNAME and CTFD_PASSWORD; these fields take precedence over stale tokens/sessions.
• Auth priority: username/password first, then token, then session cookie. Lower-priority credentials are ignored when a higher-priority option is present.

Support / feedback

If something breaks or you have questions, reach out:

• Telegram: @ismailgaleev
• Jabber: ismailgaleev@chat.merlok.ru
• Email: umbra2728@gmail.com

Testing

• Run uv run pytest.
• Timeouts are configurable via env: CTFD_TIMEOUT (total), CTFD_CONNECT_TIMEOUT, CTFD_READ_TIMEOUT (seconds). Defaults are 20s total / 10s connect / 15s read.

Development

• Dev dependencies: uv sync --group dev
• Lint/format: uv run ruff check . and uv run ruff format .
• Tests: uv run pytest
• Pre-commit: uv run pre-commit install (see CONTRIBUTING.md)

License

Apache-2.0. See LICENSE.