VulnerabilityPublished 26 Oct 2026Updated 27 Oct 2026

CVE-2026-99085: Linux kernel · sched_ext: Fix CPU hotplug hang when a dying CPU's tasks sit in the BPF scheduler

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-99085· High

Not known to be exploited.

Data as of 28 Oct 2026, 01:30 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10linux`pkg:deb/ubuntu/linux?arch=source&distro=stonking`Other threats	Affected 7.0.0-14.14 – 7.3.0-9.9 6 affected builds	Fixed in–
Ubuntu 26.10linux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonking`Other threats	Affected =7.0.0-1004.4 =7.3.0-1002.3 =7.3.0-1003.4	Fixed in–
Ubuntu 26.10linux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-oracle`pkg:deb/ubuntu/linux-oracle?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this issue is available and should be applied by updating to patched Linux kernel versions. The vendor advisory indicates that the problem is resolved by changes to the scheduler code that ensure tasks are properly re-enqueued and dispatched during CPU hotplug. Systems running affected kernel versions should upgrade to fixed releases to prevent CPU hotplug hangs.

Description

CVE-2026-99085 is a Linux kernel vulnerability affecting the CPU hotplug process when tasks managed by the BPF scheduler remain on a CPU that is going offline. This can cause the CPU hotplug thread to hang, potentially stalling the CPU offline operation. The issue arises because tasks on the BPF scheduler are still counted on the CPU's runqueue, but the CPU no longer dispatches these tasks, leading to a deadlock scenario. The fix involves re-enqueuing tasks on the local dequeue and ensuring dispatch continues until the runqueue goes offline.

Impact

The vulnerability can cause the CPU hotplug process to hang indefinitely, potentially leading to system instability or degraded performance during CPU offline operations. This may affect systems relying on CPU hotplug functionality, such as dynamic CPU scaling or maintenance operations. There is no indication of remote code execution or privilege escalation. No known exploits in the wild have been reported.

Summary

This vulnerability in the Linux kernel's scheduler extension (sched_ext) causes the CPU hotplug process to hang when a CPU is taken offline while tasks are still assigned to it within the BPF scheduler. Normally, the CPU hotplug thread waits for its runqueue to empty before completing the CPU offline process. However, tasks on user dequeue structures or held by the BPF scheduler remain counted on the runqueue but are not dispatched once the CPU becomes inactive. This results in either the hotplug thread never waking or the offline process stalling until external intervention occurs. The patch addresses this by re-enqueuing tasks on the local dequeue of the dying CPU and modifying dispatch behavior to continue until the runqueue is fully offline, preventing the hang.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Oct 2026, 01:30 UTC

Technical details

References

Community reviews

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