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()`

GitPython spawns the real git binary with an argument vector built from caller-supplied values. To prevent argument injection, GitPython maintains denylists of “unsafe” Git options (--upload-pack, --receive-pack, --exec, -c, --config, …) that can be abused to run arbitrary commands, and enforces them with Git.check_unsafe_options().

That enforcement is only wired into the network commands — clone_from, Remote.fetch, Remote.pull, Remote.push. Several other public APIs that also forward caller-controlled values into the git argv have no guard at all:

1. Repo.archive(ostream, treeish=None, prefix=None, **kwargs) forwards **kwargs verbatim into git archive. An attacker-influenced options mapping such as {"remote": ".", "exec": "<cmd>"} becomes git archive --remote=. --exec=<cmd> -- <treeish>, and git archive --remote=<local repo> invokes git-upload-archive whose path is overridden by --exec → arbitrary command execution under default Git configuration (no protocol.ext.allow needed).

2. repo.git.ls_remote(<url>, upload_pack="<cmd>") (and the dynamic-command builder generally) turns the upload_pack kwarg into --upload-pack=<cmd> with no guard → arbitrary command execution.

3. Repo.iter_commits(rev) and Repo.blame(rev, file) place the caller’s rev value into the argv before the -- end-of-options separator and apply no leading-dash check. A benign-looking ref value such as --output=/path/to/file is parsed by git rev-list / git blame as the --output option, which opens and truncates an arbitrary file before Git even validates the revision → arbitrary file clobber (integrity/availability; can destroy keys, configs, lockfiles, or be aimed at files the host later sources).

The first two are direct code execution; the third is an arbitrary file-overwrite primitive. All share one root cause: the check_unsafe_options / end-of-options discipline that GitPython applies to clone/fetch/pull/push was never extended to these sinks.