CVE-2019-5421 is a critical-severity (CVSS 9.8) CWE-367 vulnerability in devise. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for devise — see the affected versions and patch details below.
devise Time-of-check Time-of-use Race Condition vulnerability
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
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 | 4.6.0bundle update devise --conservative |
Affected Products
deviseplataformatecResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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.
Frequently Asked Questions
Is CVE-2019-5421 in your dependencies?
Find it across RubyGems, including transitive dependencies.