sched/core: Make core-sched flips wait for in-flight selections
CVE-2026-89520 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 7.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89520?
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Who is affected
- Linux Linux: 539f65125d20aacab54d02d77f10a839f45b09dc to < a2a16896ed53046f275f56a6cd8ca3fb6f12c4f3, 539f65125d20aacab54d02d77f10a839f45b09dc to < 3e2511bffa93a639774a99e392181e21d28677e2, 539f65125d20aacab54d02d77f10a839f45b09dc to < 9d69422ddaa13526c2223444e237d948d6e44728, 539f65125d20aacab54d02d77f10a839f45b09dc to < 23eda24f325a6e6d686d30ec75f2e9d6745e2015
- Linux Linux: 5.14
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/a2a16896ed53046f275f56a6cd8ca3fb6f12c4f3
- git.kernel.org/stable/c/3e2511bffa93a639774a99e392181e21d28677e2
- git.kernel.org/stable/c/9d69422ddaa13526c2223444e237d948d6e44728
- git.kernel.org/stable/c/23eda24f325a6e6d686d30ec75f2e9d6745e2015
- git.kernel.org/stable/c/f3629c63a4af3e491381780bc6c123cb498c4c40
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON