Security Audit: 2 finding(s) in mcp-server-filesystem

AgentAudit Security Audit Report

Overall Assessment

The MCP filesystem server is well-designed with strong security practices. The codebase demonstrates professional security implementation including:

✅ Comprehensive path validation with symlink resolution
✅ Strict directory access control via allowlist
✅ Atomic file operations preventing race conditions
✅ Proper handling of null bytes and path traversal attempts
✅ Detailed security comments explaining design decisions

The 2 low-severity findings are minor improvements that don't represent exploitable vulnerabilities.

Real Findings (2 low-severity issues)

1. LOW: Error messages expose internal path information

File: src/filesystem/lib.ts:87
Issue: Error messages include full filesystem paths when validation fails
Impact: Could leak directory structure in shared environments
Remediation: Consider sanitizing error messages in production mode

2. LOW: NPX usage without version pinning in documentation

File: README.md:243
Issue: Documentation shows npx -y @modelcontextprotocol/server-filesystem without version pinning
Impact: Supply chain risk if malicious version published
Remediation: Update docs to recommend version pinning for production: npx -y @modelcontextprotocol/server-filesystem@0.6.3

By-Design Security Patterns (Informational)

These are intentional features that require careful user configuration but are not vulnerabilities:

1. Broad filesystem permissions - By design for an MCP filesystem server. Users control allowed directories via configuration.
2. Arbitrary path operations - Necessary functionality for AI agent file operations. Protected by path validation.

Recommendations

1. For Documentation: Add version pinning examples to README
2. For Error Handling: Implement a debug mode flag to toggle verbose vs. sanitized errors
3. For Users: Always restrict allowed directories to minimum necessary paths; use Docker read-only mounts where possible

Full Report

View the complete audit report with code-level details and evidence:
AgentAudit Report

This audit was performed automatically by AgentAudit, the security registry for AI agent packages. The findings are based on code review of commit 70c549b.

Start with src/filesystem/lib.ts:87 to inspect how validation errors expose full paths, then review README.md:243 for the unpinned npx example. Done means the error handling has an agreed production-safe behavior and the documentation recommends a pinned package version.