Gen0Sec WAF Rule MCP Server

WAF & Smart-Firewall Rule Generation for Agentic LLMs

An MCP server that lets an LLM author, validate, and test Wirefilter WAF and Smart Firewall rules — grounded in live schema and real CVE exploit templates instead of guesswork.

What it does:

• Validates rules against a real engine — expressions are checked (and optionally test-matched) through the Wirefilter rules-validator API, so the model gets real pass/fail feedback, not a hallucinated opinion

• Grounds generation in live schema — serves the authoritative actions / expressions / fields / functions / operators / values straight from the rules-validator, so rules use fields that actually exist

• Pulls real exploit context — fetches CVE-indexed Nuclei templates from multiple sources (Nuclei Open Source via GitHub, Nuclei Paid via the ProjectDiscovery API) to inform CVE-driven rule generation

• Self-updating — periodically refreshes the Wirefilter context and CVE template repositories in the background

Runs anywhere Python 3.12+ runs · ships as a Claude Desktop bundle, a stdio MCP server, or an HTTP container

Related MCP server: crowdsec-local-mcp

Quick start

Claude Desktop (bundle)

# Prerequisites: mcpb (npm install -g @anthropic-ai/mcpb)
make pack          # produces the thin, portable gen0sec-mcp-server.mcpb

Open the generated gen0sec-mcp-server.mcpb file — Claude Desktop installs it in about a minute, after which the tools, resources, and prompts are available.

Which bundle: thin vs offline

The GitHub release ships two .mcpb files:

• gen0sec-mcp-server.mcpb (thin, default) — carries no native wheels, so it runs on any supported interpreter. On first launch it builds a small private virtualenv from requirements.txt, which needs one-time network access to PyPI. Nothing global is touched, and the host Python is never modified.

• gen0sec-mcp-server-offline.mcpb (air-gapped) — carries prebuilt wheels for several interpreter targets under server/lib/<abi-tag>/ (CPython 3.12–3.13 on macOS arm64, Linux x86_64/aarch64, Windows x86_64). On a covered target it starts with no network access. On an uncovered interpreter it degrades to the thin bundle's first-run venv.

The extension picks the right path automatically; the only difference is whether a one-time network install can happen at first launch. Set Path to Python executable in the extension config to a Python ≥ 3.12 if the default python3 isn't suitable.

Building locally:

make pack          # thin bundle (release default)
make vendor-multi  # add this host's ABI dir to server/lib/<abi-tag>/
make pack-offline  # offline bundle from whatever ABI dirs are present

The full cross-platform offline bundle is assembled in CI, where each target is vendored natively (see .github/workflows/offline-bundle.yaml).

Cursor IDE — local (stdio)

Add to ~/.cursor/mcp.json (%USERPROFILE%\.cursor\mcp.json on Windows):

{
  "mcpServers": {
    "waf-rule-mcp": {
      "command": "uv",
      "args": [
        "run",
        "--project", "/absolute/path/to/mcp-server",
        "/absolute/path/to/mcp-server/server/main.py"
      ],
      "env": {
        "WAF_VALIDATION_API_URL": "https://public.gen0sec.com/v1/waf/validate"
      }
    }
  }
}

WAF_VALIDATION_API_URL is optional — if unset, the value from server/config.yaml is used. Restart Cursor to apply.

Docker (HTTP)

docker build -t waf-rule-mcp .
docker run -p 8000:8000 waf-rule-mcp

Then point your MCP client at it:

{
  "mcpServers": {
    "waf-rule-mcp": { "url": "http://localhost:8000" }
  }
}

The WAF rule validation API must be reachable for the validation tools to work. Set its URL via WAF_VALIDATION_API_URL or server/config.yaml.

MCP surface

Tools

Resources

Prompts

Architecture

flowchart TD
    LLM([Agentic LLM / MCP client]) <--> MCP

    subgraph MCP[Gen0Sec WAF Rule MCP Server]
        T[Tools]
        R["Resources<br/>wafcontext://*"]
        P[Prompts]
        RU[Resource updater<br/>periodic refresh]
    end

    T -->|validate / fields| RV[Wirefilter rules-validator API]
    R -->|live schema| RV
    T -->|CVE templates| CS

    subgraph CS[CVE sources]
        N1[Nuclei Open Source<br/>GitHub]
        N2[Nuclei Paid<br/>ProjectDiscovery API]
    end

    RU -.refreshes.-> CS
    RU -.refreshes.-> RV

Documentation

Thank you!

• Cloudflare for Wirefilter

• ProjectDiscovery for the Nuclei templates