CVE-2021-3820 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in i. 1 public exploit reference exists, so weaponization risk is real. A fix is available for i — see the affected versions and patch details below.
inflect vulnerable to Inefficient Regular Expression Complexity
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-3820 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 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, a proxy for how much of the ecosystem is exposed.
inpmDescription
inflect is customizable inflections for nodejs. inflect is vulnerable to Inefficient Regular Expression Complexity
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | i | all versions | 0.3.7npm install i@0.3.7 |
Affected Products
inflectinflect_projectResearch 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 i, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update i to 0.3.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3820 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-2021-3820 in your dependencies?
Find it across npm, including transitive dependencies.