Deadlock in Linux kernel - CVE-2026-99085

Vulnerability details

The vulnerability allows a local user to cause a denial of service by hanging CPU hotplug operations.

The vulnerability exists due to improper synchronization in the Linux kernel sched_ext scheduler when offlining a CPU whose tasks remain in a user dispatch queue or are held by the BPF scheduler. A local user can trigger the affected scheduling conditions during CPU offlining to prevent the hotplug thread from completing, potentially leaving cpu_down() hung while holding cpu_hotplug_lock and causing a denial of service.

Affected software

How to mitigate CVE-2026-99085

External References

• https://git.kernel.org/stable/c/173ff9d03ec6373c3158b6e630af33a9b36fd216
• https://git.kernel.org/stable/c/638ee6bca19750934ea13f9c325f46fd8ae60064
• https://git.kernel.org/stable/c/d35a535d3e3e71f92a051d94e415f43612c4edfc
• https://git.kernel.org/stable/c/f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c

Related Security Bulletins

• Deadlock in Linux kernel sched
• Debian update for linux