CVE-2026-98087 — sched/rt,dl: Skip migrate-disabled tasks when picking a push candidate
In the Linux kernel, the following vulnerability has been resolved: sched/rt,dl: Skip migrate-disabled tasks when picking a push candidate A migrate_disable()'d RT task cannot be moved to another CPU, but the scheduler still keeps such a task on that CPU's pushable list (rq->rt.pushable_tasks) and still marks the runqueue RT-overloaded (rq->rt.overloaded = 1). So the RT balancer keeps treating this CPU as having a task to move away, and keeps trying to move the task, but the push can never succeed. When the head is pinned, push_rt_task() does not give up either. It falls back to pushing rq->curr instead, using the per-CPU stopper, as added by commit a7c81556ec4d ("sched: Fix migrate_disable() vs rt/dl balancing"). The CPU spends tens of milliseconds in this retry loop. The core is isolated for real-time work, but during the loop nearly half of its time is consumed by pushes that cannot succeed. An ftrace capture of the affected CPU, with sched_switch enabled and commit 94894c9c477e ("sched/rt: Skip currently executing CPU in rto_next_cpu()") applied, shows where the CPU time went. Two SCHED_FIFO tasks at equal priority shared the CPU, taskA migrate_disable()'d and queued, taskB as rq->curr. In one 89 ms window, taskB got only 52 ms of CPU. The other 37 ms went to the stopper thread. The scheduler kept trying to push taskA, the pinned head of the pushable list, fell back to pushing taskB instead, and woke the stopper 5204 times. Every one of those pushes failed and no task was moved. taskA stayed runnable and queued the whole time, and never ran. Pushing taskB fails on a re-check. find_lock_lowest_rq() drops the rq lock to take the target rq lock, then checks again with "task != pick_next_pushable_task(rq)". The task being pushed is taskB, but the pick returns taskA, the head of the pushable list. taskB is rq->curr, and set_next_task_rt() removes the running task from that list, so taskB can never be the head. The check expects a candidate taken from the pushable list, but the fallback pushes rq->curr, which is never on that list. So the check fails every time. .--> push-IPI arrives | | | v | pushable head = taskA -> pinned, cannot be pushed | | | v | so push taskB instead -> wake migration/N, a stop-class | | thread, so it preempts taskB | v | re-check compares taskB against the pushable head, | which is still taskA -> give up | | | v | nothing moved, taskA still queued, rq still overloaded | | '----------' repeats every ~17 us, 5204 times, for 89 ms The loop cannot stop itself. Every round leaves the runqueue exactly as it was, so the next push-IPI does the same thing. In the capture it ended only when taskB went to sleep on its own. taskA was then picked locally and left the pushable list. CPU time per task in the window, from sched_switch: taskB 51.95 ms real work migration/N 37.18 ms nothing moved taskA 0.00 ms queued the whole time, never picked idle 0.01 ms Counts over the same window: 7667 push-IPIs handled on this CPU 17481 pick_next_pushable_task() returned taskA, still pinned 5204 find_lock_lowest_rq() gave up on the re-check 1 push that actually completed 0 migrations of taskA The CPU times and the window length come from the standard sched_switch tracepoint. The counts needed tracepoints added inside the RT balancer for this investigation. The self-IPI path is closed by the rto_next_cpu() fix above, and that part works. But the runqueue is still marked overloaded, because the pinned task is still advertised as pushable. Other CPUs now send the push-IPIs during their own RT balancing, and the same loop runs again. Closing the self-IPI path did not stop a pinn ---truncated---
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux | ≥ a7c81556ec4d341dfdbf2cc478ead89d73e474a7 and < 755476d7ba92a1f3fe2a376c515d710bc6baebc3≥ a7c81556ec4d341dfdbf2cc478ead89d73e474a7 and < b0c6f947057751ab4d30ccf8095cd19804fb97fa≥ a7c81556ec4d341dfdbf2cc478ead89d73e474a7 and < dae5c0292080dd7b9c7d784268dcf443f1f3d15eversion 5.11 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Not enough vector or weakness data: use the affected application’s logs as a starting point.
Timeline
What happened to this CVE, newest first.
- 2026
- Record published
- Affected products added · linux/linux
- Source status changed · → Undergoing Analysis
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
3 on the record
Elsewhere on this site
Related CVEs (same products)
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- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 2d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 2d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 2d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 2d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CVSS score published by NVD, the CNA, CISA or GitHub so far.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-98087 is "sched/rt,dl: Skip migrate-disabled tasks when picking a push candidate", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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