CVE-2019-5421
CRITICALCVE-2019-5421 is a critical-severity (CVSS 9.8) CWE-367 vulnerability in devise. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2019-5421 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
devise Time-of-check Time-of-use Race Condition vulnerability
Blast Radius
deviseReal-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
Plataformatec Devise version 4.5.0 and earlier, using the lockable module contains a CWE-367 vulnerability in The Devise::Models::Lockable class, more specifically at the #increment_failed_attempts method. File location: lib/devise/models/lockable.rb that can result in Multiple concurrent requests can prevent an attacker from being blocked on brute force attacks. This attack appear to be exploitable via Network connectivity - brute force attacks. This vulnerability appears to have been fixed in 4.6.0 and later.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | devise | all versions | 4.6.0 |
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 devise. 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 devise to 4.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-5421 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-2019-5421 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-2019-5421. 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-2019-5421 in your dependencies?
O3 detects CVE-2019-5421 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.