# CVE-2021-42385: Use after free in busybox

> A use-after-free in BusyBox awk allows attackers to cause denial of service or potentially execute code via crafted patterns.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Nov 2021
- **Updated:** 3 Nov 2025
- **Also known as:** ALPINE-CVE-2021-42385, AZL-6351, DEBIAN-CVE-2021-42385, GHSA-px6h-65pj-6gq3, UBUNTU-CVE-2021-42385

## What is CVE-2021-42385?

CVE-2021-42385 is a high-severity use after free vulnerability in Fedoraproject Fedora, published on 15 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official 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 evaluate function

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-42385?

It affects 2 products.


Products: Busybox Busybox, Fedoraproject Fedora.

## How do I fix CVE-2021-42385?

Apply the vendor's patch.

## Is CVE-2021-42385 being exploited?

There is no known exploitation of CVE-2021-42385 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2022-48174](https://insights.sbomify.com/CVE-2022-48174/): Memory corruption in n/a (critical 9.8)
- [CVE-2021-42377](https://insights.sbomify.com/CVE-2021-42377/): Memory corruption in busybox (critical 9.8)
- [CVE-2016-2148](https://insights.sbomify.com/CVE-2016-2148/): Memory corruption in n/a (critical 9.8)
- [CVE-2022-28391](https://insights.sbomify.com/CVE-2022-28391/): Command injection in n/a (high 8.8)
- [CVE-2017-16544](https://insights.sbomify.com/CVE-2017-16544/): Code injection in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42385 and fix it if it is affected.

What it is: CVE-2021-42385 is a high-severity use after free vulnerability in Fedoraproject Fedora, published on 15 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-42385 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-42385/ (Markdown: https://insights.sbomify.com/CVE-2021-42385/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42385
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42385
- OSV: https://osv.dev/vulnerability/CVE-2021-42385

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42385/
Summaries are generated and may contain mistakes; the official description above is the record.