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CVE-2026-99065— cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： cgroup/cpuset：处理 guarantee_active_cpus() 中的 CPU 热插拔竞态问题 在提交 2125c0034c5d（"cgroup/cpuset：使 cpuset 热插拔处理变为同步"）中，cpuset 的热插拔操作被改为同步执行。该提交同时移除了用于处理 cpuset_hotplug_work 与 CPU 热插拔通知器之间竞态的代码，其假设是此时竞态问题已不复存在。 随后，提交 7a0aabd9ce69（"cgroup/cpuset：始终

AI Predicted 7.8 Difficulty: Hard EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 7a0aabd9ce697fc581ec691b21f748050fbcf004< 8d88d3221204fbb1b6dc2c0f2f2181fe49126639 affected
7a0aabd9ce697fc581ec691b21f748050fbcf004< a21c255159bfe0034740292e10d2e258feeeb10d affected
7a0aabd9ce697fc581ec691b21f748050fbcf004< 23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2 affected
6.16 affected
< 6.16 unaffected
6.18.57≤ 6.18.* unaffected
7.2.11≤ 7.2.* unaffected
7.3≤ * unaffected
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I. Basic Information for CVE-2026-99065

Vulnerability Information
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Vulnerability Title
cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus() With commit 2125c0034c5d ("cgroup/cpuset: Make cpuset hotplug processing synchronous"), the cpuset hotplug operation becomes synchronous. That commit also removes the code that handles race between cpuset_hotplug_work and cpu hotplug notifier with the assumption that race is now gone. Later commit 7a0aabd9ce69 ("cgroup/cpuset: Always use cpu_active_mask") updates the cpuset code to always use cpu_active_mask instead of cpu_online_mask in some places including guarantee_online_cpus() which is renamed to guarantee_active_cpus() in that commit. In the case of CPU offline operation, cpu_active_mask is updated first in sched_cpu_deactivate() to remove the offline CPU before cpuset_handle_hotplug() is called to update the effective_cpus of the affected cpusets. The cpu_online_mask is updated after that near the end of the offline operation to remove the offline CPU. As a result, the race comes back and the top cpuset may not have any active CPU leading to NULL pointer dereference during the race window when guarantee_active_cpus() is called after cpu_active_mask is updated to remove the CPU to be torn down but before cpuset_handle_hotplug() is able to properly update the effective_cpus of the top cpuset. Fix this by adding back the NULL cs check to avoid this problem.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 7a0aabd9ce697fc581ec691b21f748050fbcf004 ~ 8d88d3221204fbb1b6dc2c0f2f2181fe49126639 -
Linux Linux 6.16 -

II. Public POCs for CVE-2026-99065

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III. Intelligence Information for CVE-2026-99065

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Patches & Fixes for CVE-2026-99065 (3)

Same Patch Batch · Linux · 2026-10-23 · 217 CVEs total

CVE-2026-98959 9.8 CRITICAL btrfs: fix xattr replace when multiple xattrs are packed in the same item
CVE-2026-99078 9.8 CRITICAL net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry
CVE-2026-99079 9.8 CRITICAL net/mlx5e: Prevent stale XSK buffer release on refill retry
CVE-2026-98988 8.8 HIGH namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE
CVE-2026-99083 8.8 HIGH ksmbd: fix heap out-of-bounds write in krb5_authenticate()
CVE-2026-99082 8.8 HIGH KVM: x86: Use active memslots for the per-vCPU MMIO cache
CVE-2026-98981 8.8 HIGH namespace: unhash a dentry before detaching the mounts on it
CVE-2026-98980 8.8 HIGH namei: don't reveal overmounted entries in refwalk
CVE-2026-98870 8.8 HIGH ksmbd: remove stale channels from all sessions on teardown
CVE-2026-99042 8.4 HIGH io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
CVE-2026-98978 8.4 HIGH namespace: never expire a locked mount
CVE-2026-99064 8.1 HIGH cipso: adjust cached option offsets when removing CIPSO
CVE-2026-98968 8.1 HIGH amt: send the relay's General Query directly from the receive path
CVE-2026-99016 7.8 HIGH riscv: futex: untag the user pointer before the atomic access
CVE-2026-98999 7.8 HIGH drm/xe: Fix stale pinned_link entry when fb-pin performs the final unpin
CVE-2026-99054 7.8 HIGH tipc: destroy topsrv workqueues before closing connections
CVE-2026-99014 7.8 HIGH Bluetooth: hci_sync: Fix command skb lifetime during scan setup
CVE-2026-99053 7.8 HIGH tipc: hold a reference to nodes found by link name
CVE-2026-98945 7.8 HIGH HID: steam: Rearrange teardown sequence
CVE-2026-99051 7.8 HIGH fsverity: RCU-delay the freeing of struct fsverity_info

Showing top 20 of 217 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux