GHSA-2f96-g7mh-g2hx

Command injection via long-option prefix abbreviation bypassing check_unsafe_options (incomplete fix of CVE-2026-42215 / GHSA-rpm5-65cw-6hj4)

Component: gitpython-developers/GitPython (PyPI: GitPython) Affected: all versions carrying the 3.1.47 blocklist fix, through current main (verified at commit 20c5e275, 3.1.50-42) Reporter: hackkim

Summary

The 3.1.47 fix for CVE-2026-42215 blocks dangerous git options (--upload-pack, --config, -c, -u for clone; --upload-pack for fetch/pull; --receive-pack, --exec for push) so callers cannot reach command-executing options unless they pass allow_unsafe_options=True.

The fix canonicalizes an option name along one axis (underscore→hyphen via dashify) and checks it against an exact-match dict. It does not account for git's unambiguous long-option prefix abbreviation. Git accepts any unambiguous prefix of a long option (--upload-p, --upload-pa, --upload-pac all resolve to --upload-pack). So a kwarg key like upload_p canonicalizes to upload-p, misses the blocklist dict, and is emitted to git as --upload-p=<value> → executed as --upload-pack=<value> → command injection, in the default allow_unsafe_options=False configuration.

The asymmetry (root cause)

# git/cmd.py (commit 20c5e275), lines 948-974
@classmethod
def _canonicalize_option_name(cls, option):
    option_name = option.lstrip("-").split("=", 1)[0]
    option_tokens = option_name.split(None, 1)
    if not option_tokens:
        return ""
    return dashify(option_tokens[0])      # only transform: "_" -> "-"

@classmethod
def check_unsafe_options(cls, options, unsafe_options):
    canonical_unsafe_options = {cls._canonicalize_option_name(o): o for o in unsafe_options}
    for option in options:
        unsafe_option = canonical_unsafe_options.get(cls._canonicalize_option_name(option))
        if unsafe_option is not None:
            raise UnsafeOptionError(...)

The guard...