GHSA-fjr4-x663-mwxc is a high-severity (CVSS 8.1) CWE-88 vulnerability in gitpython. O3 Security confirms whether GHSA-fjr4-x663-mwxc is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
GitPython: Arbitrary file overwrite via git diff --output argument injection in Diffable.diff (key- and value-controlled)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fjr4-x663-mwxc.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-fjr4-x663-mwxc plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 368,770 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
gitpythonReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | gitpython | all versions | 3.1.54 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gitpython. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update gitpython to 3.1.54 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fjr4-x663-mwxc is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fjr4-x663-mwxc is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fjr4-x663-mwxc. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This is an Important arbitrary file overwrite vulnerability in GitPython's Diffable.diff method. It allows an attacker to write arbitrary content to chosen file paths at the process's privilege level by manipulating git options, which could lead to system compromise or privilege escalation.
Frequently Asked Questions
Is GHSA-fjr4-x663-mwxc in your dependencies?
O3 detects GHSA-fjr4-x663-mwxc across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.