# CVE-2021-3713: Memory corruption in QEMU

> A malicious guest user can trigger an out-of-bounds write in QEMU's UAS emulation to crash the host or execute arbitrary code.

- **Severity:** High 7.4 (`CVSS:3.1/AV:P/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2021
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-6831, DEBIAN-CVE-2021-3713, GHSA-q4w6-2g7p-pr2c, OESA-2021-1348, UBUNTU-CVE-2021-3713

## What is CVE-2021-3713?

CVE-2021-3713 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 25 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An out-of-bounds write flaw was found in the UAS (USB Attached SCSI) device emulation of QEMU in versions prior to 6.2.0-rc0. The device uses the guest supplied stream number unchecked, which can lead to out-of-bounds access to the UASDevice->data3 and UASDevice->status3 fields. A malicious guest user could use this flaw to crash QEMU or potentially achieve code execution with the privileges of the QEMU process on the host.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-3713?

It affects 2 products.


Products: Debian Debian Linux, Qemu Qemu.

## How do I fix CVE-2021-3713?

Upgrade to a fixed version.

## Is CVE-2021-3713 being exploited?

There is no known exploitation of CVE-2021-3713 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3713 and fix it if it is affected.

What it is: CVE-2021-3713 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 25 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3713 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-3713/ (Markdown: https://insights.sbomify.com/CVE-2021-3713/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3713
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3713
- OSV: https://osv.dev/vulnerability/CVE-2021-3713

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3713/
Summaries are generated and may contain mistakes; the official description above is the record.