Security Audit: Unconstrained string parameters across all official servers

[manja316]

Summary

I ran automated security audits on 7 official MCP servers using mcp-security-audit. All servers scored Grade A or B (85-100/100), which is great. But there's one consistent finding across every server except mcp-server-fetch:

No string parameters use maxLength, pattern, or enum constraints.

Findings

Server	Score	Unconstrained Strings
Fetch	100/100	0
SQLite	95/100	5 (SQL queries, table names)
Time	95/100	4 (timezone identifiers)
GitHub	94/100	Multiple
Memory	92/100	1 (search query)
Git	90/100	18 (paths, messages, branches)
Filesystem	85/100	Multiple (paths)

Why this matters

1. DoS vector — Unconstrained strings accept arbitrarily long input. A 10MB commit message or 50K-char file path must be processed by the server.
2. No boundary validation — If an LLM is compromised via prompt injection, the tool schema provides no defense against malformed input.
3. Network transports — With MCP supporting Streamable HTTP, servers may be network-exposed where these constraints become critical.

Suggested fix

One line per parameter:

{
  "name": "path",
  "type": "string",
  "maxLength": 4096
}

For known-format params:

{
  "name": "timezone",
  "type": "string",
  "pattern": "^[A-Za-z_/]+$",
  "maxLength": 50
}

Full reports

Individual JSON/text reports for each server: LuciferForge/mcp-audit-reports

The audit tool: pip install mcp-security-audit

Happy to discuss findings or help with fixes.