BREW-BTCLI-CVE-2026-73624 (GHSA-FJR4-X663-MWXC)

Vulnerability from osv_homebrew – Published: 2026-08-14 08:53 – Updated: 2026-10-07 22:51 – Source website
VLAI
Summary
GitPython: Arbitrary file overwrite via git diff --output argument injection in Diffable.diff (key- and value-controlled)
Details

Summary

Diffable.diff() forwards **kwargs straight into diff/diff_tree with no check_unsafe_options guard. Diffable is mixed into Commit, Tree, IndexFile, and Submodule, giving a broad surface. git diff --output=<path> writes real patch content to an attacker-chosen path, enabling arbitrary file overwrite.

Root Cause

diff.py:188-283 builds and runs the diff command with no check_unsafe_options anywhere in the method (grep-confirmed). Additionally diff.py:265 does args.insert(0, other), placing the caller-supplied other ref BEFORE the -- separator, so a value of --output=/path is parsed by git as an option — a value-only control path requiring no kwarg key.

Impact

Overwrite/corrupt any file at process privilege with attacker-chosen path (e.g. ~/.ssh/authorized_keys, configs, lockfiles). Content is real diff/patch bytes (attacker-influenced). Per the skill's rule, controlling WHICH file is overwritten = I:H regardless of content constraints.

Proof of Concept

# Key-control:
commit.diff(other_commit, output='/home/app/.ssh/authorized_keys')   # victim overwritten with diff (105 bytes verified)
# Value-control (attacker controls only the ref string):
commit.diff(other='--output=/home/app/.ssh/authorized_keys')          # 14-byte victim -> 146 bytes of diff-tree output

Attack Chain

  1. Entry (value-control): commit.diff(other=<user ref>) with other = "--output=/home/app/.ssh/authorized_keys". Guard: none in Diffable.diff. Bypass proof: no check_unsafe_options in the method body (grep); other inserted pre--- at diff.py:265.
  2. Sink: git diff-tree <sha> --output=/home/app/.ssh/authorized_keys -r ... -> git opens+truncates the target then writes diff content. Impact: overwrite/corrupt any file at process privilege (attacker chooses the path). Verified argv and victim overwrite live.

Bypass Evidence

Live-verified on HEAD (tag 3.1.53): both key-control (output=) and value-control (other='--output=...') overwrote a victim file with real diff-tree content; argv confirmed ['git','diff-tree','<sha>','--output=/victim','-r',...]. This is the same value-control model GHSA-956x deemed fix-worthy for iter_commits(rev='--output=') — but diff is a distinct, unguarded sink NOT touched by that fix.

Affected Versions

<= 3.1.53

Suggested Fix

Add check_unsafe_options to Diffable.diff (mirroring iter_commits/archive), and/or place --end-of-options before the other ref so it cannot be parsed as an option.

Reported by zx (Jace) — GitHub: @manus-use

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": "3.1.54"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "btcli",
        "purl": "pkg:brew/btcli"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "9.5.1"
            }
          ],
          "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`Diffable.diff()` forwards `**kwargs` straight into `diff`/`diff_tree` with **no** `check_unsafe_options` guard. `Diffable` is mixed into `Commit`, `Tree`, `IndexFile`, and `Submodule`, giving a broad surface. `git diff --output=\u003cpath\u003e` writes real patch content to an attacker-chosen path, enabling arbitrary file overwrite.\n\n## Root Cause\n`diff.py:188-283` builds and runs the diff command with no `check_unsafe_options` anywhere in the method (grep-confirmed). Additionally `diff.py:265` does `args.insert(0, other)`, placing the caller-supplied `other` ref BEFORE the `--` separator, so a value of `--output=/path` is parsed by git as an option \u2014 a value-only control path requiring no kwarg key.\n\n## Impact\nOverwrite/corrupt any file at process privilege with attacker-chosen path (e.g. `~/.ssh/authorized_keys`, configs, lockfiles). Content is real diff/patch bytes (attacker-influenced). Per the skill\u0027s rule, controlling WHICH file is overwritten = I:H regardless of content constraints.\n\n## Proof of Concept\n```python\n# Key-control:\ncommit.diff(other_commit, output=\u0027/home/app/.ssh/authorized_keys\u0027)   # victim overwritten with diff (105 bytes verified)\n# Value-control (attacker controls only the ref string):\ncommit.diff(other=\u0027--output=/home/app/.ssh/authorized_keys\u0027)          # 14-byte victim -\u003e 146 bytes of diff-tree output\n```\n\n## Attack Chain\n1. Entry (value-control): `commit.diff(other=\u003cuser ref\u003e)` with `other = \"--output=/home/app/.ssh/authorized_keys\"`. Guard: none in `Diffable.diff`. Bypass proof: no `check_unsafe_options` in the method body (grep); `other` inserted pre-`--` at diff.py:265.\n2. Sink: `git diff-tree \u003csha\u003e --output=/home/app/.ssh/authorized_keys -r ...` -\u003e git opens+truncates the target then writes diff content. Impact: overwrite/corrupt any file at process privilege (attacker chooses the path). Verified argv and victim overwrite live.\n\n## Bypass Evidence\nLive-verified on HEAD (tag 3.1.53): both key-control (`output=`) and value-control (`other=\u0027--output=...\u0027`) overwrote a victim file with real diff-tree content; argv confirmed `[\u0027git\u0027,\u0027diff-tree\u0027,\u0027\u003csha\u003e\u0027,\u0027--output=/victim\u0027,\u0027-r\u0027,...]`. This is the same value-control model GHSA-956x deemed fix-worthy for `iter_commits(rev=\u0027--output=\u0027)` \u2014 but `diff` is a distinct, unguarded sink NOT touched by that fix.\n\n## Affected Versions\n`\u003c= 3.1.53`\n\n## Suggested Fix\nAdd `check_unsafe_options` to `Diffable.diff` (mirroring `iter_commits`/`archive`), and/or place `--end-of-options` before the `other` ref so it cannot be parsed as an option.\n\n---\nReported by **zx (Jace)** \u2014 GitHub: @manus-use",
  "id": "BREW-btcli-CVE-2026-73624",
  "modified": "2026-10-07T22:51:32Z",
  "published": "2026-08-14T08:53:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/security/advisories/GHSA-fjr4-x663-mwxc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/pull/2180"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/commit/1d51b891d7f236044a6aa17498ec682b63dad6e6"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gitpython-developers/GitPython"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gitpython-developers/GitPython/releases/tag/3.1.54"
    }
  ],
  "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: Arbitrary file overwrite via git diff --output argument injection in Diffable.diff (key- and value-controlled)",
  "upstream": [
    "GHSA-fjr4-x663-mwxc",
    "CVE-2026-73624",
    "PYSEC-2026-3995"
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.