mcp_resource_server

CRITICAL VULNERABILITY: The server is vulnerable to path traversal (arbitrary file read). The `_download_file_bytes` function directly constructs a file path from the `file_id` when `RESOURCE_SERVER_URL_PATTERN` uses the `file://` protocol. An attacker controlling the `file_id` parameter (e.g., through MCP tool calls like `get_file('../../etc/passwd')`) can read arbitrary files on the host filesystem outside the intended `/mnt/resources` directory. For example, passing `../../../../etc/passwd` as `file_id` would lead to the server reading `/etc/passwd`. This vulnerability allows unauthorized access to sensitive system files. There is also potential for SSRF if `RESOURCE_SERVER_URL_PATTERN` is misconfigured to allow external URL input.