Description

GitPython: git-config section-name injection enables arbitrary config directives (core.sshCommand RCE)

Summary

In GitPython <= 3.1.52, the config writer neutralizes only CR, LF, and NUL in configuration names, but writes section names into the [...] header with no other escaping. A section/subsection name that contains ] [ " closes the intended header and opens a second same-line section, injecting an arbitrary config directive — with no newline required. Because a submodule name is attacker-controlled data (it comes from a repository's .gitmodules, or from an application that lets a user name a submodule) and is written verbatim into the parent repository's trusted .git/config, an attacker can set core.sshCommand (or alias.*, core.pager, core.fsmonitor) and achieve remote code execution on the victim's next git operation. Likely CWE-74 (Injection).

This is a distinct variant of the injection addressed by GHSA-mv93-w799-cj2w / GHSA-v87r-6q3f-2j67: those fixed newline injection into config values/names (patched in 3.1.50); the [r\n\x00] guard added for them does not stop a same-line section break inside a name.

Details

The only guard applied to section/option names before writing is _assure_config_name_safe, which uses a regex that matches solely CR/LF/NUL:

git/config.py:75,897-899 (GitPython 3.1.52):

UNSAFE_CONFIG_CHARS_RE = re.compile(r"[\r\n\x00]")
...
def _assure_config_name_safe(self, name: "cp._SectionName", label: str) -> None:
    if isinstance(name, str) and UNSAFE_CONFIG_CHARS_RE.search(name):
        raise ValueError("Git config %s names must not contain CR, LF, or NUL" % label)

The name is then serialized into the header with no escaping of ], [, ", space, = or #:

git/config.py:693:

fp.write(("[%s]\n" % name).encode(defenc))

For submodules the name is wrapped as submodule "<name>" (git/objects/submodule/util.py:39, return f'submodule "{name}"'), which supplies the balancing quote. A submodule named:

x"] [core] sshCommand=CMD #

therefore serializes to the header [submodule "x"] [core] sshCommand=CMD #"]. git parses everything after the first ] on that line as a fresh section, yielding core.sshCommand=CMD (the trailing #"] is an inline comment). No CR/LF/NUL appears, so _assure_config_name_safe never fires.

The attacker-controlled name reaches this sink through documented public entry points that write it into the parent repository's .git/config:

Repo.create_submodule(name=<untrusted>, ...) → Submodule.add → git/objects/submodule/base.py:619 writer.set_value(sm_section(name), "url", url) — a single call, no hostile remote required.

Repo.clone_from(<hostile url>) + repo.submodule_update(init=True) → git/objects/submodule/base.py:855 writer.set_value(sm_section(self.name), "url", self.url), where self.name is read unvalidated from the cloned repo's .gitmodules.

Asymmetry: the sibling class is blocked — a newline in a config value, e.g. set_value("core", "editor", "x\n\tsshCommand=CMD"), raises ValueError. The section-name bracket payload is not caught by the same guard.

PoC

Single self-contained script, run against the pinned release in an ephemeral environment. Non-destructive: the injected value is an inert marker, verified parse-only with git config --get; no ssh/fetch/push is run and nothing is executed.

#!/usr/bin/env python3
"""Minimal PoC: git-config section-name injection in GitPython==3.1.52."""
from importlib.metadata import version
import os, tempfile, subprocess
import git

print(f"# GitPython {version('GitPython')}")        # version proof -- first line
...
Show more

Run:

uv run --with GitPython==3.1.52 python poc.py

Observed output:

# GitPython 3.1.52
control name : 'docs'
  git core.sshCommand -> (1, '') (unset)
exploit name : 'x"] [core] sshCommand=MARKER_9f3a #'
  written header      -> [submodule "x"] [core] sshCommand=MARKER_9f3a #"]
  git core.sshCommand -> (0, 'MARKER_9f3a')
VERDICT: attacker-controlled submodule name injected core.sshCommand=MARKER_9f3a into the victim's trusted .git/config (git would run it on the next ssh op)

The benign name yields a single clean [submodule "docs"] section; the malicious name yields an injected core.sshCommand. Deterministic across runs. The payload must use balanced double-quotes (an unbalanced " makes git reject the header); the submodule "<name>" wrapper balances them automatically.

Impact

Arbitrary attacker-controlled write into the victim's repository-local .git/config, which git fully trusts. core.sshCommand is executed as the ssh transport command on the victim's next ssh git operation (fetch/pull/push), giving remote code execution; other injectable keys (alias.*, core.pager, core.fsmonitor) fire on more common operations. Reachable in default configuration through two realistic paths:

an application that constructs a submodule from untrusted input via Repo.create_submodule(name=...) (single call); or

Repo.clone_from of an untrusted repository followed by submodule_update — the canonical submodule threat model, where the malicious name is read from the cloned .gitmodules.

No non-default git settings are required. Primarily a Unix vector: on Windows the " in the resulting .git/modules/<name> directory name can abort the fresh-clone write branch (the direct config-API and create_submodule sinks are unaffected).

Recommended fix

Reject or escape configuration section/subsection/option names that contain ], [, ", or leading/trailing whitespace (or apply git's own section-name escaping) in _assure_config_name_safe / write_section, rather than only CR/LF/NUL. Validating submodule names before they reach sm_section would additionally close the clone-driven path.

Mitigation

Aliases

References