CVE-2026-89519
Received Received - Intake

Race Condition in Linux Kernel Sched Ext

Vulnerability report for CVE-2026-89519, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Replace SCX_RQ_BAL_KEEP with a dispatch verdict return SCX_RQ_BAL_KEEP tells the pick to keep running the previous task, a leftover from when balancing and picking were separate operations. An rq-level flag only works while dispatches and picks pair up one to one, which core scheduling breaks: selections interleave through dispatch's lock drops and a pick can consume a stale flag, keeping a task that has since been dequeued. Fixing core scheduling support requires the decision to travel with the dispatch that made it. Make scx_dispatch_sched() and balance_one() return an explicit verdict instead and drop the flag's plumbing from the tools autogen enum headers. Also factor the pick-side invocation, its follow-up queueing and the post-dispatch checks out of do_pick_task_scx() into dispatch_pick(). No functional changes intended. v2: Drop the SCX_RQ_BAL_KEEP plumbing from the tools autogen enum headers as well (Andrea).

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Meta Information

Published
2026-09-11
Last Modified
2026-09-11
Generated
2026-09-12
AI Q&A
2026-09-11
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

Helpful Resources

Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability related to the sched_ext subsystem. It involves replacing an old flag SCX_RQ_BAL_KEEP with a dispatch verdict return to fix issues in core scheduling. The problem occurs when balancing and picking operations are separated, leading to stale flags keeping dequeued tasks running. The fix ensures decisions travel with the dispatch that made them.

Detection Guidance

This vulnerability is specific to the Linux kernel's sched_ext subsystem and does not have a direct detection method or commands provided in the context. It requires kernel-level inspection for core scheduling issues.

Impact Analysis

This vulnerability could lead to incorrect task scheduling in the Linux kernel, potentially causing system performance issues or unexpected behavior. It may affect systems using core scheduling features, especially those with multiple tasks competing for CPU resources.

Mitigation Strategies

Update the Linux kernel to the patched version that resolves this issue. Monitor kernel releases for fixes related to sched_ext and core scheduling.

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