Affected: gitpython-developers GitPython

GitPython before 3.1.50 fails to validate newline characters in the section parameter of config_writer(), allowing attackers to inject arbitrary section headers into .git/config. Attackers can inject newlines to create a forged [core] section with hooksPath pointing to attacker-controlled directories, achieving remote code execution when git hooks are triggered.

Affected: PyPI: GitPython

Summary

The patch for CVE-2026-42215 (GitPython 3.1.49) validates newlines only in the value parameter of set_value(). The section and option parameters are passed to configparser without any newline validation. An attacker who controls the section argument can inject \n to write arbitrary section headers into .git/config, including a forged [core] section with hooksPath pointing to an attacker-controlled directory, leading to RCE when any git hook is triggered.

Details

File: git/config.py — GitPython 3.1.49 (latest patched version)

```python def set_value(self, section: str, option: str, value) -> "GitConfigParser": value_str = self._value_to_string_safe(value) # only value is validated if not self.has_section(section): self.add_section(section) # section not validated super().set(section, option, value_str) # option not validated return self ```

_write() formats section headers as "[%s]\n" % name. When section = "user]\n[core", this writes [user]\n[core]\n — two valid section headers — into .git/config.

PoC

```python import git, os, subprocess

repo = git.Repo.init("/tmp/bypass_test")

os.makedirs("/tmp/evil_hooks", exist_ok=True) with open("/tmp/evil_hooks/pre-commit", "w") as f: f.write("#!/bin/sh\nid > /tmp/rce_proof.txt\n") os.chmod("/tmp/evil_hooks/pre-commit", 0o755)

# Inject newline into section parameter (not value — already patched) with repo.config_writer() as cw:…

Affected: PyPI: gitpython

GitPython before 3.1.50 fails to validate newline characters in the section parameter of config_writer(), allowing attackers to inject arbitrary section headers into .git/config. Attackers can inject newlines to create a forged [core] section with hooksPath pointing to attacker-controlled directories, achieving remote code execution when git hooks are triggered.