CVE-2021-27884
MEDIUMCVE-2021-27884 is a medium-severity (CVSS 5.1) Insufficient Random Values vulnerability in yapi-vendor. O3 Security confirms whether CVE-2021-27884 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Weak JSON Web Token in yapi-vendor
Blast Radius
yapi-vendorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Weak JSON Web Token (JWT) signing secret generation in YMFE YApi through 1.9.2 allows recreation of other users' JWT tokens. This occurs because Math.random in Node.js is used.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | yapi-vendor | all versions | 1.9.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yapi-vendor. 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 yapi-vendor to 1.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-27884 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-2021-27884 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-2021-27884. 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-2021-27884 in your dependencies?
O3 detects CVE-2021-27884 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.