VulnerabilityPublished 23 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 CVE Database V5

Not known to be exploited · fixed in f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:18 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c, d35a535d3e3e71f92a051d94e415f43612c4edfc, 638ee6bca19750934ea13f9c325f46fd8ae60064 +1

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

Upgrade Linux kernel to f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c, d35a535d3e3e71f92a051d94e415f43612c4edfc, 638ee6bca19750934ea13f9c325f46fd8ae60064 or 173ff9d03ec6373c3158b6e630af33a9b36fd216.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ f0e1a0643a59bf1f922fa209cec86a170b784f3f, < f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c	Fixed in f79cd7a2df3768323fbfb9b0f96adff08fb7eb4c
LinuxLinux	Affected ≥ f0e1a0643a59bf1f922fa209cec86a170b784f3f, < d35a535d3e3e71f92a051d94e415f43612c4edfc	Fixed in d35a535d3e3e71f92a051d94e415f43612c4edfc
LinuxLinux	Affected ≥ f0e1a0643a59bf1f922fa209cec86a170b784f3f, < 638ee6bca19750934ea13f9c325f46fd8ae60064	Fixed in 638ee6bca19750934ea13f9c325f46fd8ae60064
LinuxLinux	Affected ≥ f0e1a0643a59bf1f922fa209cec86a170b784f3f, < 173ff9d03ec6373c3158b6e630af33a9b36fd216	Fixed in 173ff9d03ec6373c3158b6e630af33a9b36fd216
LinuxLinux	Affected =6.12	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel versions identified by the fixed commit hashes. Systems running the affected version (=6.12) should upgrade to a fixed kernel version containing these commits. No additional mitigation is required beyond applying the official patch.

Description

CVE-2026-99085 is a Linux kernel vulnerability affecting CPU hotplug handling in the sched_ext scheduler. It causes a hang during CPU hotplug when tasks associated with a dying CPU remain in the BPF scheduler's runqueue. The issue arises because the dying CPU's hotplug thread waits indefinitely for its runqueue to empty, but tasks held by the BPF scheduler prevent this, leading to a deadlock or stall. The fix involves re-enqueuing tasks on the local deferred scheduling queue (DSQ) when the runqueue goes offline and ensuring dispatch continues until the runqueue is fully offline.

Impact

The vulnerability causes a system hang or stall during CPU hotplug operations, potentially leading to a denial of service condition on affected Linux systems. Specifically, the CPU hotplug thread can deadlock waiting for tasks to be migrated off a CPU that is going offline, or the CPU offline process can stall indefinitely if tasks are affine only to the dying CPU and held by the BPF scheduler. This impacts system stability during CPU hotplug events.

Summary

This vulnerability in the Linux kernel's sched_ext scheduler causes a CPU hotplug hang when a CPU is taken offline while tasks remain assigned to it in the BPF scheduler. Normally, the CPU hotplug thread waits for its runqueue to empty before completing the CPU shutdown. However, sched_ext counts tasks on the runqueue even if they are on a user DSQ or held by the BPF scheduler, but the inactive CPU no longer dispatches tasks, causing the runqueue to never empty. This results in the hotplug thread hanging indefinitely or the CPU offline process stalling until external intervention. The patch modifies the scheduler to re-enqueue tasks on the local DSQ when the runqueue goes offline and keeps dispatch running 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 26 Oct 2026, 09:53 UTC

Technical details

References

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