CVE-2021-21267
HIGHCVE-2021-21267 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in schema-inspector. 3 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-21267 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Regular Expression Denial-of-Service in npm schema-inspector
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.
schema-inspectornpmDescription
Schema-Inspector is an open-source tool to sanitize and validate JS objects (npm package schema-inspector). In before version 2.0.0, email address validation is vulnerable to a denial-of-service attack where some input (for example a@0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.) will freeze the program or web browser page executing the code. This affects any current schema-inspector users using any version to validate email addresses. Users who do not do email validation, and instead do other types of validation (like string min or max length, etc), are not affected. Users should upgrade to version 2.0.0, which uses a regex expression that isn't vulnerable to ReDoS.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | schema-inspector | all versions | 2.0.0 |
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 schema-inspector. 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 schema-inspector to 2.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21267 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-2021-21267 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-2021-21267. 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-2021-21267 in your dependencies?
O3 detects CVE-2021-21267 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.