CVE-2026-98864
Received Received - Intake

Linux Kernel Race Condition in Sched Ext

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics") moved the final ops_state store in scx_dispatch_enqueue() after the DSQ unlock so that the custody update and ops.dequeue() precede it. A task can thus be found on a DSQ while still SCX_OPSS_DISPATCHING. The dequeue and core-sched pick paths wait for the state to clear in ops_dequeue() but the reenqueue paths don't. A reenqueue in that window runs ops.enqueue() and sets SCX_OPSS_QUEUED before the dispatch has completed. The dispatcher's final store then overwrites it with SCX_OPSS_NONE and finish_dispatch() drops every later dispatch of the task. Wait for SCX_OPSS_DISPATCHING to clear before dequeueing a task for reenqueue, the same way ops_dequeue() does.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98864
EUVD
EUVD-2026-103804

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
Linux Linux ebf1ccff79c43f860cbd2f9d6cfab9a462d0cb2d
Linux Linux ebf1ccff79c43f860cbd2f9d6cfab9a462d0cb2d
Linux Linux 7.1

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability in the sched_ext subsystem. It involves a race condition where a task can be reenqueued before the dispatcher completes its operation. The issue occurs because the reenqueue paths do not wait for the SCX_OPSS_DISPATCHING state to clear, unlike the dequeue paths. This can cause the dispatcher to drop later dispatches of the task.

Impact Analysis

This vulnerability may lead to task scheduling issues, where tasks are not properly dispatched or executed. It could cause system instability, performance degradation, or unexpected behavior in applications relying on the Linux kernel's scheduling mechanisms.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the sched_ext issue. Monitor kernel logs for tasks being reenqueued prematurely. Ensure no custom kernel modules or configurations rely on the vulnerable behavior.

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