# CVE-2021-40426: Memory corruption in libsox

> A heap-based buffer overflow in libsox allows attackers to execute arbitrary code or cause denial of service via a specially crafted file.

- **Severity:** Critical 10.0 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Apr 2022
- **Updated:** 15 Apr 2025
- **Also known as:** DEBIAN-CVE-2021-40426, GHSA-5x4j-m9qh-g9w5, UBUNTU-CVE-2021-40426

## What is CVE-2021-40426?

CVE-2021-40426 is a critical memory corruption vulnerability in Sound Exchange libsox, published on 14 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A heap-based buffer overflow vulnerability exists in the sphere.c start_read() functionality of Sound Exchange libsox 14.4.2 and master commit 42b3557e. A specially-crafted file can lead to a heap buffer overflow. An attacker can provide a malicious file to trigger this vulnerability.

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2021-40426?

It affects 1 product.


Products: Sound Exchange Project Sound Exchange.

## How do I fix CVE-2021-40426?

Apply the vendor's patch.

## Is CVE-2021-40426 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40426 exists.

## Other vulnerabilities in Sound Exchange libsox

- [CVE-2021-3643](https://insights.sbomify.com/CVE-2021-3643/): Information disclosure in sox (critical 9.1)
- [CVE-2021-23159](https://insights.sbomify.com/CVE-2021-23159/): Memory corruption in SoX (Sound eXchange) (medium 5.5)
- [CVE-2021-23172](https://insights.sbomify.com/CVE-2021-23172/): Memory corruption in SoX (Sound eXchange) (medium 5.5)
- [CVE-2021-23210](https://insights.sbomify.com/CVE-2021-23210/): Denial of service in SoX (Sound eXchange) (medium 5.5)
- [CVE-2021-33844](https://insights.sbomify.com/CVE-2021-33844/): Denial of service in SoX (Sound eXchange) (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40426 and fix it if it is affected.

What it is: CVE-2021-40426 is a critical memory corruption vulnerability in Sound Exchange libsox, published on 14 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40426 exists.

Affected product: Sound Exchange libsox. 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-2021-40426/ (Markdown: https://insights.sbomify.com/CVE-2021-40426/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40426
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40426
- OSV: https://osv.dev/vulnerability/CVE-2021-40426

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40426/
Summaries are generated and may contain mistakes; the official description above is the record.