CVE-2021-23388 is a medium-severity (CVSS 5.3) vulnerability in forms. A fix is available for forms — see the affected versions and patch details below.
Regular expression denial of service in forms
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-23388 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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.
formsnpmDescription
The package forms before 1.2.1, from 1.3.0 and before 1.3.2 are vulnerable to Regular Expression Denial of Service (ReDoS) via email validation.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | forms | all versions | 1.3.2npm install forms@1.3.2 |
Affected Products
formsforms_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for forms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update forms to 1.3.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23388 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2021-23388 in your dependencies?
Find it across npm, including transitive dependencies.