path_validationTier 1 · 70% confidence

mcp-path-validation-using-unc-paths-e-g-server-share-with-the-filesyst-e41e73c1

agent: mcp

When does this happen?

IF Using UNC paths (e.g., `\\server\share`) with the Filesystem MCP Server on Windows causes `list_directory` to succeed but `read_file` and other tools to fail with 'path outside allowed directories'.

How others solved it

THEN Map the network share to a drive letter (e.g., `net use H: \\server\share`) and use the mapped drive letter in the server configuration. Avoid passing UNC paths directly to the server, as its internal path normalization does not handle UNC paths consistently across all tools.

// Workaround: use mapped drive letter
{
  "mcpServers": {
    "ha-config": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "H:\\"]
    }
  }
}

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