What’s Vulnerable › Vulnerabilities

CVE-2021-43138: Prototype Pollution in async

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2022-04-06 · updated 2026-06-17
• Weakness: CWE-1321

Description

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 products

• Async Project Async: before 2.6.4; from 3.0.0 before 3.2.2 — fixed in 2.6.4, 3.2.2
• Fedoraproject Fedora: 36, 37
• Npm Async: from 3.0.0 before 3.2.2; from 2.0.0 before 2.6.4 — fixed in 3.2.2, 2.6.4

How to fix

Upgrade to a fixed version: Async Project Async 2.6.4, 3.2.2; Npm Async 3.2.2, 2.6.4. Check the vendor advisory for mitigations.

References

• https://github.com/caolan/async/blob/master/lib/internal/iterator.js
• https://github.com/caolan/async/blob/master/lib/mapValuesLimit.js
• https://github.com/caolan/async/blob/v2.6.4/CHANGELOG.md#v264
• https://github.com/caolan/async/commit/e1ecdbf79264f9ab488c7799f4c76996d5dca66d
• https://github.com/caolan/async/compare/v2.6.3...v2.6.4
• https://github.com/caolan/async/pull/1828
• https://jsfiddle.net/oz5twjd9/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MTEUUTNIEBHGKUKKLNUZSV7IEP6IP3Q3/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UM6XJ73Q3NAM5KSGCOKJ2ZIA6GUWUJLK/
• https://security.netapp.com/advisory/ntap-20240621-0006/
• https://github.com/caolan/async/blob/master/lib/internal/iterator.js
• https://github.com/caolan/async/blob/master/lib/mapValuesLimit.js

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