CVE-2021-4241 is a medium-severity (CVSS 5.3) CWE-331 vulnerability in phpservermon/phpservermon. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-4241 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
PHPServerMon PRNG has Insufficient Entropy
Real-World Exposure
phpservermon/phpservermonReal-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
A vulnerability, which was classified as problematic, was found in phpservermon. Affected is the function setUserLoggedIn of the file src/psm/Service/User.php. The manipulation leads to use of predictable algorithm in random number generator. The exploit has been disclosed to the public and may be used. The name of the patch is bb10a5f3c68527c58073258cb12446782d223bc3. It is recommended to apply a patch to fix this issue. The identifier of this vulnerability is VDB-213744.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | phpservermon/phpservermon | all versions | 3.6.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpservermon/phpservermon. 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 phpservermon/phpservermon to 3.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4241 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 CVE-2021-4241 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 CVE-2021-4241. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-4241 in your dependencies?
O3 detects CVE-2021-4241 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.