CVE-2026-99105
sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ
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.
INFO
Published Date :
Oct. 28, 2026, 11:17 a.m.
Last Modified :
Oct. 28, 2026, 11:17 a.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the latest secure version.
- Apply the specific patch for sched_ext task enqueuing.
- Verify rescheduling logic after the update.
- Monitor system stability and performance.
References to Advisories, Solutions, and Tools
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CVE-2026-99105.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-99105 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-99105
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Oct. 28, 2026
Action Type Old Value New Value Added 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. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99105.json">CVE-2026-99105</a> Added Reference https://git.kernel.org/stable/c/396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59 Added Reference https://git.kernel.org/stable/c/7a9df76679633cf26e0fea882a684012c6ec245a Added Reference https://git.kernel.org/stable/c/8d891c218016b6145993e082e7f732cb69dd0e29