CVE-2026-76218: GitPython Unguarded Git Option Forwarding Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9rj7-rf2p-w77r",
  "modified" : "2026-09-08T20:54:14Z",
  "published" : "2026-08-07T15:36:43Z",
  "aliases" : [ "CVE-2026-76218" ],
  "summary" : "GitPython: Unguarded git option forwarding in Repo.init enables arbitrary command execution via --template clone hooks",
  "details" : "## Summary\n`Repo.init()` forwards `**kwargs` verbatim to `git init` with no unsafe-option guard and no `allow_unsafe_options` parameter. `git init --template=<dir>` copies `<dir>/hooks/*` into the new repo's `.git/hooks`, so an attacker-controlled `template` kwarg plants a hook that executes on the next git operation → arbitrary code execution. `--template` is already recognized as unsafe for clone (it is on `unsafe_git_clone_options`, and GHSA-6p8h-3wgx-97gf covers the clone path), but `Repo.init` is a distinct method that never received a guard and needs an independent fix.\n\n## Root Cause\n`Repo.init(path, mkdir, odbt, expand_vars, **kwargs)` is a bare `git.init(**kwargs)` (git/repo/base.py:1435) with no `check_unsafe_options` and no `allow_unsafe_options`.\n\n## Impact\nArbitrary code execution (hook fires on next git op) at the privileges of the host process. Two preconditions raise attack complexity (AC:H): the app must forward a `template=` kwarg (KEY control) AND the attacker must stage an executable hook directory at a known path — the same profile GHSA-6p8h-3wgx-97gf accepted as HIGH for the clone path. Default `allow_unsafe_options` is irrelevant here because `Repo.init` has no guard at all.\n\n## Proof of Concept\n```python\n# attacker stages /evil/hooks/post-commit (executable)\nfrom git import Repo\nRepo.init(path, template=\"/evil\")\n# next commit runs /evil/hooks/post-commit -> ACE\n```\n\n## Attack Chain\n1. Entry: attacker stages `/evil/hooks/post-commit` (executable) and gets the app to call `Repo.init(path, template='/evil')`.\n2. Check: NONE on `Repo.init`. Bypass proof: base.py:1435 is a bare `git.init(**kwargs)`. argv (observed): `['git','init','--template=/evil']`.\n3. Sink: git copies `/evil/hooks/post-commit` → `<repo>/.git/hooks/post-commit`.\n4. Impact: next commit runs the hook → arbitrary code execution.\n\n## Bypass Evidence\nIndependently reproduced (gate harness): `Repo.init(dst, template='<evil>')` → argv `['git','init','--template=<evil>']` unguarded; hook copied into `.git/hooks/post-commit`; after `git commit` the `INIT_ACE` marker was created. `--separate-git-dir=<path>` is a parallel arbitrary-redirect vector through the same unguarded sink (value control only).\n\n## Affected Versions\n`GitPython <= 3.1.57` (unguarded `git.init(**kwargs)` present verbatim on the latest release tag).\n\n## Suggested Fix\nAdd a `check_unsafe_options` guard (with an `allow_unsafe_options` parameter) to `Repo.init`, consulting a denylist that includes `--template` and `--separate-git-dir` (path-taking / hook-installing options).\n\n---\nReported by **zx (Jace)** — GitHub: @manus-use",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "GitPython"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.58"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.1.57"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-9rj7-rf2p-w77r"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-76218"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/pull/2204"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/commit/d9ddb55bdc66"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gitpython-developers/GitPython"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/releases/tag/3.1.58"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/gitpython-before-remote-code-execution-via-repo-init"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-88", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-07T15:36:43Z",
    "nvd_published_at" : null
  }
}