GHSA-6p8h-3wgx-97gf: GitPython Incomplete Unsafe_git_clone_options Denylist Omits --template Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6p8h-3wgx-97gf",
  "modified" : "2026-07-24T16:42:09Z",
  "published" : "2026-07-24T16:42:09Z",
  "aliases" : [ ],
  "summary" : "GitPython: Incomplete unsafe_git_clone_options denylist omits --template enabling arbitrary command execution via clone hooks",
  "details" : "## Summary\nGitPython's `unsafe_git_clone_options` denylist omits `--template`. `git clone --template=<dir>` copies `<dir>/hooks/` into the new repository and runs them (`post-checkout` fires during clone), so a caller who can influence clone options can achieve arbitrary command execution in the default `allow_unsafe_options=False` configuration.\n\n## Root Cause\n`base.py:145-152` defines `unsafe_git_clone_options = [\"--upload-pack\",\"-u\",\"--config\",\"-c\"]` — `--template` is absent. The guard candidate `['--template']` passes `check_unsafe_options` (verified). git copies the hook directory and executes `post-checkout` at checkout time. git's `protocol.allow`/`GIT_ALLOW_PROTOCOL` do not gate `--template`; the incomplete denylist is the only defense.\n\n## Impact\nArbitrary OS command execution during clone (default config). Requires an attacker-readable directory containing an executable hook — a genuine second precondition (realistic via shared filesystems, upload dirs, `/tmp`, or attacker-writable network paths), reflected as AC:H.\n\n## Proof of Concept\n```python\n# attacker stages <dir>/hooks/post-checkout (chmod +x)\nfrom git import Repo\nRepo.clone_from(src, dst, template='<dir>')   # post-checkout hook executes -> marker created (verified)\n```\n\n## Attack Chain\n1. Setup: attacker stages `<dir>/hooks/post-checkout` (chmod +x). Guard: n/a (filesystem).\n2. Entry: `Repo.clone_from(url, path, template='<dir>')`. Guard: `check_unsafe_options(candidates=['--template'], unsafe=unsafe_git_clone_options)`. Bypass proof: `--template` not on the denylist -> passes (verified candidate `['--template']`, no error).\n3. Sink: git copies the hook and executes `post-checkout` at checkout. Impact: ACE, default config (verified marker created).\n\n## Bypass Evidence\nLive-verified on HEAD (tag 3.1.53): guard candidate `['--template']` passed with no error; staged `post-checkout` hook executed during `clone_from`, creating the marker. Independent of the value-smuggle bypass (`--template` is a legitimate long option that survives any single-char-value fix). Not covered by any existing advisory.\n\n## Affected Versions\n`<= 3.1.53`\n\n## Suggested Fix\nAdd `--template` (and audit for other hook/exec-influencing options) to `unsafe_git_clone_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" : "3.1.54"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.1.53"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-6p8h-3wgx-97gf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/pull/2180"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/commit/ffcb5359e87619f4fe4a70a4aff5f08c5580ba97"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gitpython-developers/GitPython"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/releases/tag/3.1.54"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-184", "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T16:42:09Z",
    "nvd_published_at" : null
  }
}