CVE-2026-43392
Linux Kernel Sched Ext Starvation Vulnerability
Publication date: 2026-05-08
Last updated on: 2026-05-08
Assigner: kernel.org
Description
Description
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Linux kernel's scheduler extension (sched_ext) related to the function scx_enable(). During the task switching loop from READY to ENABLED states, the calling thread's scheduling class changes from fair to ext. Since the fair class has higher priority than the ext class, workloads that saturate the fair class can indefinitely starve the enable thread, causing the system to hang.
The issue was introduced when the enable path switched from using preempt_disable() to scx_bypass(), which does not protect against starvation by fair-class tasks. Even the original preempt_disable() protection was incomplete, as in partial switch modes the calling thread could still be starved after preempt_enable() if switched to the ext class.
The fix involves offloading the enable operation to a dedicated system-wide real-time (SCHED_FIFO) kernel thread that cannot be starved by either fair or ext class tasks. This dedicated kthread is created lazily on first use and handles the enable work asynchronously, preventing starvation and system hangs.
How can this vulnerability impact me? :
This vulnerability can cause the system to hang indefinitely due to starvation of the enable thread in the Linux kernel scheduler. If your system runs workloads that heavily use the fair scheduling class, the enable thread may never get CPU time, leading to a system hang.
Such a hang can result in denial of service, making the system unresponsive and potentially causing disruption to applications and services running on the affected Linux system.
What immediate steps should I take to mitigate this vulnerability?
The vulnerability is fixed by offloading the enable body to a dedicated system-wide real-time (SCHED_FIFO) kernel thread which cannot be starved by either fair or ext class tasks.
To mitigate this vulnerability, you should update your Linux kernel to a version that includes this fix, as it addresses the starvation issue in scx_enable() by creating a dedicated kthread to handle the enable operations safely.