VCSS Calculator MCP

A lightweight, open-source MCP server for deterministic CVSS Base Score calculation, supporting CVSS 2.0, 3.0, 3.1, and 4.0 with severity classification.

GitHub
1

Hosted MCP Server

npx add-mcp 'https://cvss.my.id/mcp'

Installs into Claude Code, Codex, Cursor and more

Documentation

CVSS Calculator MCP

A lightweight CVSS Base Score calculator for AI agents, built with Go.

Version 1.0.0 Go version CI status License MCP

Website · MCP Registry · LobeHub · Glama Server · Glama Connector

Calculate and validate CVSS 2.0, 3.0, 3.1, and 4.0 Base Scores through a single MCP tool: calculate_cvss. Supports local stdio and remote Streamable HTTP.

Quick Start

Option 1 — Install Locally

Linux / macOS:

curl -fsSL https://get.cvss.my.id/install.sh | bash

Add the installed binary to your MCP client (choose one):

# Claude Code
claude mcp add --scope user cvss-calculator -- cvss-calculator-mcp

# Codex
codex mcp add cvss-calculator -- cvss-calculator-mcp

# OpenCode v2
opencode mcp add cvss-calculator --global -- cvss-calculator-mcp

Also available via GitHub Releases (including Windows) or go install github.com/alfa-reza/cvss-calculator-mcp/cmd/cvss-calculator-mcp@latest (Go 1.25+). Ensure the binary is in your PATH.

Option 2 — Free Remote MCP

No installation or API key required. Connect to https://cvss.my.id/mcp:

# Claude Code
claude mcp add --scope user --transport http cvss-calculator https://cvss.my.id/mcp

# Codex
codex mcp add cvss-calculator --url https://cvss.my.id/mcp

# OpenCode v2
opencode mcp add cvss-calculator --global --url https://cvss.my.id/mcp

Rate limit: 5 requests per minute per IP address. Use the local option to avoid this shared-service limit.

Other MCP clients (Cursor, Claude Desktop, VS Code, etc.)

Use cvss-calculator-mcp as a local stdio command, or https://cvss.my.id/mcp as a remote Streamable HTTP endpoint. Configuration formats depend on the client.

Cursor / Claude Desktop — local configuration (mcpServers):

{
  "mcpServers": {
    "cvss-calculator": { "command": "cvss-calculator-mcp" }
  }
}

For Cursor remote, use "url": "https://cvss.my.id/mcp" instead of the command entry.

VS Code — remote configuration (.vscode/mcp.json):

{
  "servers": {
    "cvss-calculator": { "type": "http", "url": "https://cvss.my.id/mcp" }
  }
}

See the client documentation for configuration locations and setup: Cursor · Claude Desktop · VS Code.

Usage

Ask your connected AI assistant:

Calculate the CVSS 3.1 Base Score for CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

The calculate_cvss tool accepts version and vector, returning a score and severity (for this example, 9.8 — Critical). Only complete Base vectors are supported; no CVE lookups or vulnerability scanning.

Self-Hosting

The Go binary uses stdio by default. For Streamable HTTP, run cvss-calculator-mcp --transport http (listens on 127.0.0.1:43871/mcp by default; customize with --listen).

License

Apache-2.0. CVSS is maintained by FIRST; this project is independent of FIRST.