Race in Linux kernel sched_ext reenqueue drops task dispatches
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Fixed
No CVSS vector from any source. Fix status from CNA.
Summary
The Linux kernel sched_ext scheduler, from version 7.1, is affected. A task can be found on a dispatch queue while its dispatch is still in progress, and reenqueuing it in that window overwrites the dispatch state, so later dispatches of the task are dropped.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
The Linux kernel is fixed in versions 7.2.10 and 7.3.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Linux (Linux) Fixed in 7.2.10, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 7 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4
- Red Hat OpenShift Container Platform 5
Timeline
- 2026-10-18 Threatist record created from CVE-2026-98864
- 2026-10-18 Alias added: GHSA-fpjr-j5w9-j6gm
- 2026-10-19 Fix available: Linux/[email protected] · CNA
- 2026-10-24 Affected versions changed · Red Hat
- 2026-10-24 CVSS score added · Red Hat
- 2026-11-06 Affected versions changed · Red Hat
References
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Sources
- CVE-2026-98864 · CVE Program
- CVE-2026-98864 · NVD
- FIRST EPSS
- GHSA-fpjr-j5w9-j6gm · GitHub Advisory Database · CC BY 4.0
- CVE-2026-98864 · Red Hat security data · CC BY 4.0
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