MCPP-AUTHN01: MCP tools listed without authentication

Family	Authentication challenge
Default severity	high
Confidence	medium
Mode	passive (default scan)
Spec revisions	all

Why it matters

Anyone who can reach the endpoint can enumerate (and likely call) the server's tools. Some servers are public on purpose, hence medium confidence; for anything that touches user or company data this is an authentication bypass.

Remediation

Require an OAuth access token on every MCP request (return 401 with a WWW-Authenticate: Bearer resource_metadata=... challenge), or document the server as intentionally public and suppress this finding with a justification.

References

• MCP 2025-11-25 Authorization
• MCP Security Best Practices

Suppressing

# .mcp-posture-ignore
[[ignore]]
check = "MCPP-AUTHN01"
target = "https://mcp.example.com/*"
justification = "Why this is acceptable here"
expires = 2026-12-31