CVE-2021-21252 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in jquery-validation. A fix is available for jquery-validation — see the affected versions and patch details below.
Regular Expression Denial of Service in jquery-validation
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-21252 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
jquery-validationnpmDescription
The jQuery Validation Plugin provides drop-in validation for your existing forms. It is published as an npm package "jquery-validation". jquery-validation before version 1.19.3 contains one or more regular expressions that are vulnerable to ReDoS (Regular Expression Denial of Service). This is fixed in 1.19.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | jquery-validation | all versions | 1.19.3npm install jquery-validation@1.19.3 |
| .NETNuGet | jQuery.Validation | all versions | 1.19.3dotnet add package jQuery.Validation --version 1.19.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jquery-validation, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update jquery-validation to 1.19.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21252 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-21252 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21252. 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-2021-21252 in your dependencies?
O3 Security finds CVE-2021-21252 across npm, NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.