GHSA-r9mr-m37c-5fr3: GitPython Unsafe Git Option Guard Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r9mr-m37c-5fr3",
  "modified" : "2026-07-24T16:42:57Z",
  "published" : "2026-07-24T16:42:57Z",
  "aliases" : [ ],
  "summary" : "GitPython: Unsafe git option guard bypass via single-character kwarg value token smuggling enables arbitrary command execution",
  "details" : "## Summary\nGitPython's `check_unsafe_options` guard (the control introduced by CVE-2026-42215 / GHSA-2f96 and hardened since) can be bypassed for **every** guarded method (`clone`/`clone_from`, `fetch`/`pull`/`push`, `ls_remote`, `iter_commits`, `blame`, `archive`) by smuggling an option token inside the VALUE of a single-character kwarg. In the default `allow_unsafe_options=False` configuration this yields arbitrary command execution via `--upload-pack`.\n\n## Root Cause\nThe guard builds its candidate option list from kwarg KEYS only: `_option_candidates([], {\"n\":\"--upload-pack=<cmd>\"})` returns `['-n']` (cmd.py:1042-1046 derives the candidate from the key, never the value). `-n` is not on the denylist, so `check_unsafe_options` passes. But `transform_kwarg('n', value, split_single_char_options=True)` (cmd.py:1600-1606) emits **two** argv tokens `['-n', '--upload-pack=<cmd>']`. git then parses the second token as `--upload-pack` and executes the attacker-supplied command. The guard never inspects the value that becomes a separate argv token.\n\n## Impact\nArbitrary OS command execution as the host process (via `--upload-pack`) in the default configuration, affecting all guarded methods since they all build candidates through the name-only `_option_candidates`.\n\n## Proof of Concept\n```python\nfrom git import Repo\nRepo.clone_from(bare_repo, out_dir, n=\"--upload-pack=touch /tmp/ACE;git-upload-pack\")\n# /tmp/ACE created -> ACE. Direct-name form upload_pack=\"...\" is correctly BLOCKED.\n```\nFile-write variant on a guarded revision command: `iter_commits('HEAD', g='--output=/path')` -> candidate `['-g']` passes, argv `['-g','--output=/path']`, victim file truncated.\n\n## Attack Chain\n1. Entry: app forwards a user-supplied options dict -> `Repo.clone_from(url, path, n=\"--upload-pack=touch /tmp/ACE;git-upload-pack\")`. Guard: `check_unsafe_options(options=_option_candidates([], kwargs), unsafe=unsafe_git_clone_options)` at base.py. Bypass proof: `_option_candidates([], {\"n\":\"--upload-pack=...\"})` -> `['-n']` (key-only), not on denylist -> no UnsafeOptionError (verified live).\n2. Transform: `transform_kwarg('n', value, split_single_char_options=True)` -> `['-n', '--upload-pack=touch /tmp/ACE;git-upload-pack']`. Guard: none (guard already passed on name-only candidate). Bypass proof: verified transform emits two tokens.\n3. Sink: `git clone -n --upload-pack='touch ...;git-upload-pack' -- <src> <dst>`; git parses and runs the second token. Impact: ACE (marker created, verified end-to-end).\n\n## Bypass Evidence\nLive-verified on HEAD (tag 3.1.53): `_option_candidates` returns key-only candidate `['-n']`; `transform_kwargs` emits the smuggled `--upload-pack=` token; clone_from with the payload created the marker file; the direct-name `upload_pack=` form raised UnsafeOptionError. All prior bypasses (GHSA-rpm5 underscore key, GHSA-2f96 long-option abbreviation, GHSA-v396 joined short option, GHSA-x2qx multi-before-split) are BLOCKED on HEAD — this is a distinct kwarg-value->separate-token vector.\n\n## Affected Versions\n`<= 3.1.53`\n\n## Suggested Fix\nMake `_option_candidates` also emit candidates derived from single-character kwarg VALUES when `split_single_char_options` is in effect, OR run `check_unsafe_options` over the fully-transformed argv rather than the reconstructed name-only candidate list.\n\n---\nReported by **zx (Jace)** — GitHub: @manus-use",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/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-r9mr-m37c-5fr3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/pull/2180"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gitpython-developers/GitPython/commit/e8d0fbf774d1f6baa3b481adfe48bd262e43b453"
  }, {
    "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-78", "CWE-88" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T16:42:57Z",
    "nvd_published_at" : null
  }
}