CVE-2021-4250 is a high-severity (CVSS 7.5) CWE-404 vulnerability in active_attr. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-4250 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
active_attr Improper Resource Shutdown or Release vulnerability
Real-World Exposure
active_attrReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
A vulnerability classified as problematic has been found in cgriego active_attr up to 0.15.2. This affects the function call of the file lib/active_attr/typecasting/boolean_typecaster.rb of the component Regex Handler. The manipulation of the argument value leads to denial of service. The exploit has been disclosed to the public and may be used. Upgrading to version 0.15.3 is able to address this issue. The name of the patch is dab95e5843b01525444b82bd7b336ef1d79377df. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-216207.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | active_attr | all versions | 0.15.4 |
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 active_attr. 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 active_attr to 0.15.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4250 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-2021-4250 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-2021-4250. 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-2021-4250 in your dependencies?
O3 detects CVE-2021-4250 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.