CVE-2026-89520

HighCVSS 7.8

Published: 11/09/2026(UTC)Updated: 19/10/2026(UTC)Translated: 12/09/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.16%

5th percentile - higher than 5% of all known CVEs

Summary

In the Linux kernel scheduler (sched/core), core scheduling's pick_next_task() operates on all sibling rqs under one acquisition of the shared core-wide lock. When a ->pick_task() releases the rq lock, every sibling __lock is momentarily free, letting __sched_core_flip(false) complete mid-selection and rebind rq_lockp() under it. The selection resumes on split locks, touching sibling state it no longer protects, and __schedule() finally releases a lock that was never taken while leaking the one that was.

Risk Assessment

This can cause scheduler state corruption and improper lock management, leading to system crash (denial of service) or potentially kernel code execution.

Recommendation

Update the Linux kernel to a version containing the fix that counts in-flight core-wide selections and makes __sched_core_flip() wait for them to drain. Until then, avoid configurations using core scheduling with pick_task implementations that release the rq lock.

Other vulnerabilities in Linux kernel (sched/core)

CVE-2026-89521High
In the Linux kernel scheduler (sched/core), core scheduling's pick_next_task() breaks when a ->pick_task() implementation can release the rq lock. The selection state derived on entry is only valid while the lock is held continuously; once a pick can drop the lock, an interleaving selection can invalidate it, leading to an incorrect committed pick or skewed forceidle accounting.

Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: sched/core: Make core-sched flips wait for in-flight selections Core scheduling's pick_next_task() operates on all sibling rqs under one acquisition of the shared core-wide lock. A ->pick_task() that releases the rq lock leaves every sibling __lock momentarily free, letting __sched_core_flip(false) complete mid-selection and rebind rq_lockp() under it. The selection resumes on the split locks, touching sibling state it no longer protects, and __schedule() finally releases a lock that was never taken while leaking the one that was. Count in-flight core-wide selections in the leader's rq->core_pick_in_flight and make __sched_core_flip() wait for the count to drain. The count only changes under the shared lock, which the flip holds while sampling, so no other ordering is needed. The wait can repeat while selections overlap, but the flip backs off between samples and flips are rare cookie-lifetime events. sched_core_cpu_deactivate() moves the count to the new leader - a stale copy left behind would bias it forever if that CPU later returns as its own leader.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS