MCP-for-Stata: Command injection via log_file_name parameter in Stata command wrapper

Summary

The log_file_name parameter in the stata_do API and CLI is directly interpolated into a Stata command string without sanitization. The security guard (GuardValidator) only scans the do-file content but does not validate this parameter. An attacker can inject arbitrary Stata commands (including shell, python, erase, etc.) by crafting a malicious log_file_name containing quotes, newlines, or Stata command separators.

Details

In src/stata_mcp/stata/stata_do/do.py, both _execute_unix_like and _execute_windows construct a Stata command string using Python f-strings:

commands = f"""
capture log close
{self.generate_log_command(log_file, is_replace)}
...
do "{dofile_path}"
...
"""

The generate_log_command method returns:

log_cmd = f'log using "{log_file.as_posix()}", {replace_clause} {log_type} name({log_type}_log)'

Where log_file is constructed from user-supplied log_name:

def generate_log_file(self, log_name: str, extension='log'):
    return self.log_file_path / f"{log_name}.{extension}"

The log_name parameter comes directly from user input (via MCP tool stata_do or CLI stata-mcp tool do) without any validation. Since the path is embedded inside double quotes in a Stata command string, an attacker can break out of the string context and inject arbitrary commands.

Additionally, generate_log_file does not prevent path traversal via log_name, allowing arbitrary file write outside the intended log directory.

Proof of Concept

When calling stata_do via MCP tool with:

{
  "dofile_path": "test.do",
  "log_file_name": "'; shell echo pwned > /tmp/pwned.txt; '"
}

The generated Stata commands become:

log using "<log_dir>/'; shell echo pwned > /tmp/pwned.txt; '.log", replace text name(text_log)

Stata interprets this as multiple commands, with shell echo pwned > /tmp/pwned.txt; executed as an arbitrary shell command.

Impact

• Remote Code Execution via shell command injection
• Arbitrary file write/overwrite via path traversal in log_name
• Complete bypass of the security guard, as the guard only validates do-file content, not wrapper parameters

Remediation / Fix

1. Apply strict allowlist validation to log_name (only alphanumeric, underscore, dot, hyphen; max 128 chars)
2. Resolve and verify the constructed log path remains within the intended log directory
3. Consider generating safe internal filenames (e.g., UUIDs) instead of accepting user-defined log names for command construction
4. Apply similar sanitization to dofile_path before embedding it into Stata command strings

References

• Issue: #74
• Fix commit: https://github.com/SepineTam/stata-mcp/commit/e6f945941ae0c7cf5e74a428e0b3dc82b396382f