CVE-2026-99105: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to ops.enqueue() instead of being kept running. Exiting tasks without SCX_OPS_ENQ_EXITING, migration disabled tasks without SCX_OPS_ENQ_MIGRATION_DISABLED and tasks on an offline rq skip ops.enqueue() and go straight to the local DSQ. This happens in put_prev_task_scx() after the pick has settled on idle, so nothing reschedules the CPU, which idles with the task queued until an unrelated wakeup lands on it or the watchdog fires. scx_mitosis, which sets SCX_OPS_ENQ_LAST without SCX_OPS_ENQ_EXITING, hit this during mass cgroup teardown: exiting tasks stuck in exit_mmap() for over 40 seconds. A task put on the local DSQ runs, as anywhere else. If the SCX_ENQ_LAST enqueue left the task on this CPU's local DSQ, set need_resched on the task being switched in, as proxy_resched_idle() does. resched_curr() would flag the task being put instead, and __schedule() clears that right after the pick.

Metrics

EPSS Probability

0.17%

5.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= f0e1a0643a59bf1f922fa209cec86a170b784f3f, < ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d; >= f0e1a0643a59bf1f922fa209cec86a170b784f3f, < 8d891c218016b6145993e082e7f732cb69dd0e29; >= f0e1a0643a59bf1f922fa209cec86a170b784f3f, < 396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59; >= f0e1a0643a59bf1f922fa209cec86a170b784f3f, < 7a9df76679633cf26e0fea882a684012c6ec245a
Linux	Linux	6.12

References

Timeline

Published: Oct 28, 2026
Last Modified: Oct 30, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-99105?

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to ops.enqueue() instead of being kept running. Exiting tasks without SCX_OPS_ENQ_EXITING, migration disabled tasks without SCX_OPS_ENQ_MIGRATION_DISABLED and tasks on an offline rq skip ops.enqueue() and go straight to the local DSQ. This happens in put_prev_task_scx() after the pick has settled on idle, so nothing reschedules the CPU, which idles with the task queued until an unrelated wakeup lands on it or the watchdog fires. scx_mitosis, which sets SCX_OPS_ENQ_LAST without SCX_OPS_ENQ_EXITING, hit this during mass cgroup teardown: exiting tasks stuck in exit_mmap() for over 40 seconds. A task put on the local DSQ runs, as anywhere else. If the SCX_ENQ_LAST enqueue left the task on this CPU's local DSQ, set need_resched on the task being switched in, as proxy_resched_idle() does. resched_curr() would flag the task being put instead, and __schedule() clears that right after the pick.

How severe is CVE-2026-99105?

Severity scoring for CVE-2026-99105 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-99105?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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