GHSA-4x34-chg5-mwjj is a medium-severity (CVSS 5.5) CWE-253 vulnerability in uu_chmod. O3 Security confirms whether GHSA-4x34-chg5-mwjj is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
chmod: recursive mode returns exit code 0 even when some files fail (last-file-wins)
Real-World Exposure
uu_chmodReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
In Chmoder::chmod() the recursive branch overwrites the running result instead of accumulating it, so the exit code reflects only the last file processed:
if self.recursive {
r = self.walk_dir_with_context(file, true); // overwrites r
} else {
r = self.chmod_file(file).and(r);
}
PoC: GNU returns 1 when a file fails; uutils returns 0 if the last entry succeeds:
$ chmod -R 0755 chmod-bug/root chmod-bug/user # GNU -> ret=1
$ uutils chmod -R 0755 chmod-bug/root chmod-bug/user # -> ret=0
Impact: scripts relying on the exit code get a false success signal while some files retained restrictive/unexpected permissions, leading to access-control misconfigurations. Recommendation: accumulate errors during traversal.
Remediation: Acknowledged by Canonical; fixed in commit abd581f6.
Reported by Zellic in the uutils coreutils Program Security Assessment (prepared for Canonical, Jan 20 2026), audited commit 3a07ffc5a9bd4c283e75afa548ba1f1957bad242. Finding 3.2. Credit: Zellic.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | uu_chmod | all versions | 0.6.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for uu_chmod. 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 uu_chmod to 0.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4x34-chg5-mwjj 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-4x34-chg5-mwjj 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-4x34-chg5-mwjj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4x34-chg5-mwjj in your dependencies?
O3 detects GHSA-4x34-chg5-mwjj across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.