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PYSEC-2026-1622

mcp-server-git argument injection in git_diff and git_checkout functions allows overwriting local files

Quick fix

PYSEC-2026-1622 — mcp-server-git: upgrade to the fixed version with the command below.

pip install --upgrade 'mcp-server-git>=2025.12.18'

Details

In mcp-server-git versions prior to 2025.12.18, the git_diff and git_checkout functions passed user-controlled arguments directly to git CLI commands without sanitization. Flag-like values (e.g., `--output=/path/to/file` for `git_diff`) would be interpreted as command-line options rather than git refs, enabling arbitrary file overwrites. The fix adds validation that rejects arguments starting with - and verifies the argument resolves to a valid git ref via rev_parse before execution. Users are advised to update to 2025.12.18 resolve this issue.

Thank you to https://hackerone.com/yardenporat for reporting.

Are you affected?

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Affected packages

PyPI/mcp-server-git
Introduced in: 0Fixed in: 2025.12.18
Fixpip install --upgrade 'mcp-server-git>=2025.12.18'

References