CVE-2021-43138
HIGHCVE-2021-43138 is a high-severity (CVSS 7.8) CWE-1321 vulnerability in async. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-43138 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Prototype Pollution in async
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
asyncnpmDescription
In Async before 2.6.4 and 3.x before 3.2.2, a malicious user can obtain privileges via the mapValues() method, aka lib/internal/iterator.js createObjectIterator prototype pollution.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | async | ≥ 3.0.0&&< 3.2.2 | 3.2.2 |
| 📦npm | async | ≥ 2.0.0&&< 2.6.4 | 2.6.4 |
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 async. 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 async to 3.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43138 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-2021-43138 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-2021-43138. 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-2021-43138 in your dependencies?
O3 detects CVE-2021-43138 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.