Security review of MCP (Model Context Protocol) server implementations and configurations. Use when auditing MCP server source code, evaluating third-party MCP servers before installation, or reviewing Claude Code MCP integrations for overpermissioning, injection risks, and data exposure.
Installation
Install with Codex or Claude Copy this prompt, paste it into Codex, Claude, or another assistant, and let it review the skill page and install it for you.
Security review of MCP (Model Context Protocol) server implementations and configurations. Use when auditing MCP server source code, evaluating third-party MCP servers before installation, or reviewing Claude Code MCP integrations for overpermissioning, injection risks, and data exposure.
license
CC-BY-4.0
MCP Server Security Review
Audit an MCP server by following the full procedure in plays/mcp-server-review.md.
Steps
Transport & Authentication — Check transport type (stdio vs HTTP/SSE), authentication on network transports, TLS enforcement, CORS policy, origin validation.
Tool Permission Audit — For each exposed tool: document what it claims to do vs what it actually does (read source). Classify as READ-ONLY, MUTATION, DESTRUCTIVE, NETWORK, or CREDENTIAL-ACCESS. Flag tools with broader capabilities than descriptions suggest, free-form inputs, or credential access.
Input Validation & Injection — For each tool parameter: check for command injection (shell interpolation), path traversal (../ in file paths), SQL injection (unparameterized queries), SSRF (user-supplied URLs hitting internal services), and template injection.
Data Exposure — Assess MCP resources for secrets/PII leakage, tool outputs for excessive data, error messages for internal paths/stack traces, and logging for sensitive data capture.
Scope & Sandboxing — Check file system restrictions, network scope (can it reach cloud metadata 169.254.169.254?), process permissions, resource limits, and dependency surface.
Supply Chain — Verify source trustworthiness, run SCA on dependencies, check for lockfiles and reproducible builds, assess update mechanism.
Client Configuration — Review MCP client config for absolute/specific server paths, minimized env var passthrough, and command injection safety in args.
Output
Server overview, tool risk matrix, findings using templates/finding.md, and specific configuration recommendations.
OWASP References
LLM01: Prompt Injection (via tool descriptions and outputs)
