# mcp-security

> Claude/Codex skill by [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md) · 20 stars · Updated 2026-07-31

Detects MCP tool handlers vulnerable to malicious inputs, hardcoded secrets, or unrestricted file/shell access. Use when writing MCP server definitions, tool schemas, or tool handler code. Also invoke when registering tools with Claude or building Claude Code extensions that expose file system, shell, or network access.

Tags: llms, security, skills

## Install

```sh
git clone https://github.com/thejefflarson/soundcheck /tmp/soundcheck && ln -s /tmp/soundcheck/.claude/skills/mcp-security ~/.claude/skills/mcp-security
```

## From README

MCP Server Security (OWASP LLM07:2025) What this checks Prevents MCP tool handlers from being exploited via malicious inputs, hardcoded secrets, unrestricted file access, or shell injection. A compromised MCP server gives attackers direct access to the host environment. Vulnerable patterns MCP tool handler that opens or reads a file path supplied directly by the caller with no allowlist or root confinement Tool handler that runs a shell command built from tool input with shell expansion enabled Hardcoded API key, token, or credential in the handler body or tool definition Tool schema declaring a string parameter with no length cap, pattern, or enum constraint Fix immediately Flag the vulnerable code and explain the risk. Then suggest a fix that establishes these properties: Tool schemas constrain every string parameter — maximum length, regex pattern, enumerated values, or rejection of additional properties. A bare string type is a blank check.

## Links

- HTML page: https://omgskills.com/library/thejefflarson/soundcheck/dot-claude/skills/mcp-security/
- GitHub: https://github.com/thejefflarson/soundcheck
- Author: [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md)

## More from this repo

- [authentication-failures](https://omgskills.com/library/thejefflarson/soundcheck/dot-claude/skills/authentication-failures/index.md) — Detects weak password storage, flawed JWT validation, sessions surviving logout, and missing MFA in authentication code.
   - [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md) · 20 stars
- [broken-access-control](https://omgskills.com/library/thejefflarson/soundcheck/dot-claude/skills/broken-access-control/index.md) — Detects missing ownership checks, broken role enforcement, and IDOR vulnerabilities that let users access other users'...
   - [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md) · 20 stars
- [concurrency-correctness](https://omgskills.com/library/thejefflarson/soundcheck/dot-claude/skills/concurrency-correctness/index.md) — Detects multi-threaded code where a lock is held across a blocking operation, lock acquisition order risks deadlock,...
   - [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md) · 20 stars