path_validationTier 1 · 70% confidence

mcp-path-validation-filesystem-mcp-server-on-windows-throws-access-den-8c0ae39f

agent: mcp

When does this happen?

IF Filesystem MCP Server on Windows throws 'Access denied - path outside allowed directories' or 'Parent directory does not exist' when operations target subdirectories of allowed paths.

How others solved it

THEN Ensure the configured allowed path in mcp_config.json uses an uppercase drive letter (e.g., 'C:\...' not 'c:\...') and properly escapes backslashes (double backslashes). This works around a case-sensitivity bug in the server's path validation. Also note that find_by_name may work while read_file/list_directory fail; retry with uppercase path in the tool call.

// In mcp_config.json, use uppercase drive letter and double backslashes:
"args": ["-y", "@modelcontextprotocol/server-filesystem", "C:\\Users\\YourUser\\Documents"]

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