gemini-bridge vulnerable to arbitrary local file read via consult_gemini_with_files inline mode

Summary

consult_gemini_with_files in inline mode read any file path supplied in the files argument without confining it to the working directory, then forwarded the contents to the Gemini CLI. Because the caller also controls query, the file contents are echoed back through the Gemini round-trip (and sent to Google), making this an arbitrary local file read.

Impact

An MCP client — or an LLM that has been prompt-injected into calling the tool — can read any file the server process can access (SSH keys, cloud credentials, .env, source) and have it disclosed via the tool response. No code execution by itself.

Affected component

• Tool: consult_gemini_with_files(query, directory, files, …), mode="inline"
• Sink: _read_file_for_inline via _prepare_inline_payload in src/mcp_server.py
• The at_command mode already confined paths; inline mode did not.

Root cause

_resolve_path returned an out-of-root path while only nullifying the display name, and _prepare_inline_payload read the file regardless. Absolute paths, .. traversal, and symlink escapes were all accepted.

Patch

Fixed in 1.3.1. _resolve_path now resolves symlinks and confines via Path.relative_to(root); inline mode skips any entry that resolves outside the working directory (the same guard at_command already enforced).

Workarounds

Upgrade to 1.3.1. Before upgrading, avoid mode="inline" with untrusted files input, or run the server with a restricted-permission user.

Credit

Reported privately by Zhihao Zhang (WPI).