brew-tach-cve-2026-73624
Vulnerability from osv_homebrew
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
- Entry (value-control):
commit.diff(other=<user ref>)withother = "--output=/home/app/.ssh/authorized_keys". Guard: none inDiffable.diff. Bypass proof: nocheck_unsafe_optionsin the method body (grep);otherinserted pre---at diff.py:265. - 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
{
"affected": [
{
"ecosystem_specific": {
"fix": "bump",
"range_state": "fixed",
"resource": "gitpython",
"resource_purl": "pkg:pypi/gitpython@3.1.62",
"upstream_fixed_in": "3.1.54"
},
"package": {
"ecosystem": "Homebrew",
"name": "tach",
"purl": "pkg:brew/tach"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.35.0_4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"database_specific": {
"confidence": "high",
"source": "matched",
"strategy": "registry",
"upstream_evidence": [
{
"ecosystem": "PyPI",
"key": "pkg:pypi/gitpython@3.1.62",
"name": "gitpython",
"resource": "gitpython",
"strategy": "registry",
"subject_version": "3.1.62"
}
]
},
"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-tach-CVE-2026-73624",
"modified": "2026-09-16T10:36:44Z",
"published": "2026-08-14T09:45:05Z",
"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"
]
}
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.
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- 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.
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