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brew-btcli-cve-2026-76219
Vulnerability from osv_homebrew
Published
2026-08-20 08:42
Modified
2026-09-10 18:57
Summary
GitPython: Unguarded git read-tree option forwarding in IndexFile.from_tree/reset/merge_tree enables arbitrary file overwrite
Details

Summary

IndexFile.from_tree, IndexFile.reset (→ from_tree) and IndexFile.merge_tree append caller-influenced treeish strings positionally to git read-tree with no unsafe-option guard, no allow_unsafe_options parameter, and no -- separator. git read-tree --index-output=<file> writes the resulting index to an arbitrary path, and last-occurrence-wins lets an injected --index-output override the method's internal temp path — clobbering an arbitrary file with a valid git-index blob. This is a distinct, never-guarded sink: commit 3af0c251 (GHSA-3f7w-8rr8-f37f) guarded only checkout_index and tag; read_tree was left unprotected (it is among the acknowledged unguarded call sites in that advisory's sweep but was never reported or fixed).

Root Cause

from_tree (index/base.py:388), reset (delegates to from_tree), and merge_tree (index/base.py:291) call repo.git.read_tree(*arg_list) with no check_unsafe_options and no --. The treeish is caller-influenced and positional.

Impact

Arbitrary file overwrite / destruction at the privileges of the host process. Content is constrained to a git-index blob (not attacker-chosen, so not RCE), but the target path is fully attacker-controlled — corrupting/truncating configs or destroying files at attacker-chosen writable locations = I:H + A:H (per the skill's "overwrite-any-path = I:H" rule). Pure VALUE control (positional treeish). Default configuration.

Proof of Concept

IndexFile.from_tree(repo, "--index-output=/home/victim/.bashrc")
# target overwritten with a valid git-index blob (DIRC...)

Attack Chain

  1. Entry: app calls IndexFile.from_tree(repo, treeish) / reset(commit=…) / merge_tree(base=…, rhs=…) with attacker treeish="--index-output=/home/victim/.bashrc".
  2. Check: NONE — the methods have no allow_unsafe_options and never call check_unsafe_options.
  3. Sink: repo.git.read_tree(*arg_list) — no --. argv (from_tree, observed): ['git','read-tree','--index-output=<tmp>','--index-output=/…/victim'] (last-wins).
  4. Impact: target path created/overwritten with a valid git-index blob; existing content destroyed.

Bypass Evidence

Independently reproduced (gate harness): IndexFile.from_tree(repo,'--index-output=<victim>') → victim overwritten; before=IMPORTANT ORIGINAL CONTENT, after starts DIRC\x00\x00\x00\x02… (destructive clobber, valid index blob). reset(commit=…) and both merge_tree positionals verified. Fix-commit read: 3af0c251 touched only checkout_index+tag; read_tree untouched on HEAD.

Affected Versions

GitPython <= 3.1.57 (sinks present verbatim on the latest release tag).

Suggested Fix

Add a check_unsafe_options guard (with an allow_unsafe_options parameter) to from_tree/reset/merge_tree, and/or place a -- separator before the positional treeish arguments; block --index-output (a path-taking option) on this sink.

Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "gitpython",
        "resource_purl": "pkg:pypi/gitpython@3.1.51",
        "upstream_fixed_in": "3.1.58"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "btcli",
        "purl": "pkg:brew/btcli"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/gitpython@3.1.51",
        "name": "gitpython",
        "resource": "gitpython",
        "strategy": "registry",
        "subject_version": "3.1.51"
      }
    ]
  },
  "details": "## Summary\n`IndexFile.from_tree`, `IndexFile.reset` (\u2192 from_tree) and `IndexFile.merge_tree` append caller-influenced treeish strings positionally to `git read-tree` with no unsafe-option guard, no `allow_unsafe_options` parameter, and no `--` separator. `git read-tree --index-output=\u003cfile\u003e` writes the resulting index to an arbitrary path, and last-occurrence-wins lets an injected `--index-output` override the method\u0027s internal temp path \u2014 clobbering an arbitrary file with a valid git-index blob. This is a distinct, never-guarded sink: commit `3af0c251` (GHSA-3f7w-8rr8-f37f) guarded only `checkout_index` and `tag`; `read_tree` was left unprotected (it is among the acknowledged unguarded call sites in that advisory\u0027s sweep but was never reported or fixed).\n\n## Root Cause\n`from_tree` (index/base.py:388), `reset` (delegates to from_tree), and `merge_tree` (index/base.py:291) call `repo.git.read_tree(*arg_list)` with no `check_unsafe_options` and no `--`. The treeish is caller-influenced and positional.\n\n## Impact\nArbitrary file overwrite / destruction at the privileges of the host process. Content is constrained to a git-index blob (not attacker-chosen, so not RCE), but the target path is fully attacker-controlled \u2014 corrupting/truncating configs or destroying files at attacker-chosen writable locations = I:H + A:H (per the skill\u0027s \"overwrite-any-path = I:H\" rule). Pure VALUE control (positional treeish). Default configuration.\n\n## Proof of Concept\n```python\nIndexFile.from_tree(repo, \"--index-output=/home/victim/.bashrc\")\n# target overwritten with a valid git-index blob (DIRC...)\n```\n\n## Attack Chain\n1. Entry: app calls `IndexFile.from_tree(repo, treeish)` / `reset(commit=\u2026)` / `merge_tree(base=\u2026, rhs=\u2026)` with attacker `treeish=\"--index-output=/home/victim/.bashrc\"`.\n2. Check: NONE \u2014 the methods have no `allow_unsafe_options` and never call `check_unsafe_options`.\n3. Sink: `repo.git.read_tree(*arg_list)` \u2014 no `--`. argv (from_tree, observed): `[\u0027git\u0027,\u0027read-tree\u0027,\u0027--index-output=\u003ctmp\u003e\u0027,\u0027--index-output=/\u2026/victim\u0027]` (last-wins).\n4. Impact: target path created/overwritten with a valid git-index blob; existing content destroyed.\n\n## Bypass Evidence\nIndependently reproduced (gate harness): `IndexFile.from_tree(repo,\u0027--index-output=\u003cvictim\u003e\u0027)` \u2192 victim overwritten; before=`IMPORTANT ORIGINAL CONTENT`, after starts `DIRC\\x00\\x00\\x00\\x02\u2026` (destructive clobber, valid index blob). `reset(commit=\u2026)` and both `merge_tree` positionals verified. Fix-commit read: `3af0c251` touched only `checkout_index`+`tag`; `read_tree` untouched on HEAD.\n\n## Affected Versions\n`GitPython \u003c= 3.1.57` (sinks present verbatim on the latest release tag).\n\n## Suggested Fix\nAdd a `check_unsafe_options` guard (with an `allow_unsafe_options` parameter) to `from_tree`/`reset`/`merge_tree`, and/or place a `--` separator before the positional treeish arguments; block `--index-output` (a path-taking option) on this sink.",
  "id": "BREW-btcli-CVE-2026-76219",
  "modified": "2026-09-10T18:57:19Z",
  "published": "2026-08-20T08:42:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-4gmw-gg2m-w46p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-76219"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/pull/2204"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/commit/9b5dcaf85da5946dbf69dcd53f9edba08f760b32"
    },
    {
      "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-arbitrary-file-overwrite-via-read-tree"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "GitPython: Unguarded git read-tree option forwarding in IndexFile.from_tree/reset/merge_tree enables arbitrary file overwrite",
  "upstream": [
    "GHSA-4gmw-gg2m-w46p",
    "CVE-2026-76219",
    "PYSEC-2026-3838"
  ]
}



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