GHSA-9f46-5r25-5wfm is a critical-severity (CVSS 9.8) CWE-367 vulnerability in league/flysystem. O3 Security confirms whether GHSA-9f46-5r25-5wfm is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem
Real-World Exposure
league/flysystem🐘league/flysystemReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The whitespace normalisation using in 1.x and 2.x removes any unicode whitespace. Under certain specific conditions this could potentially allow a malicious user to execute code remotely.
The conditions:
- A user is allowed to supply the path or filename of an uploaded file.
- The supplied path or filename is not checked against unicode chars.
- The supplied pathname checked against an extension deny-list, not an allow-list.
- The supplied path or filename contains a unicode whitespace char in the extension.
- The uploaded file is stored in a directory that allows PHP code to be executed.
Given these conditions are met a user can upload and execute arbitrary code on the system under attack.
Patches
The unicode whitespace removal has been replaced with a rejection (exception).
The library has been patched in:
- 1.x: https://github.com/thephpleague/flysystem/commit/f3ad69181b8afed2c9edf7be5a2918144ff4ea32
- 2.x: https://github.com/thephpleague/flysystem/commit/a3c694de9f7e844b76f9d1b61296ebf6e8d89d74
Workarounds
For 1.x users, upgrade to 1.1.4. For 2.x users, upgrade to 2.1.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | league/flysystem | all versions | 1.1.4 |
| 🐘Packagist | league/flysystem | ≥ 2.0.0&&< 2.1.1 | 2.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for league/flysystem. 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 league/flysystem to 1.1.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9f46-5r25-5wfm 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-9f46-5r25-5wfm 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-9f46-5r25-5wfm. 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-9f46-5r25-5wfm in your dependencies?
O3 detects GHSA-9f46-5r25-5wfm across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.