{"apiVersion":"1.0","identifier":"CVE-2026-99065","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.","publishedAt":"2026-10-23T13:17:30","lastModifiedAt":"2026-10-23T13:17:30","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-99065","cvssScore":null,"cvssVector":null,"epssProbability":0.00166,"riskScore":null,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-99065","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-99065","en":"https://www.redsauce.net/en/cves/CVE-2026-99065","fr":"https://www.redsauce.net/fr/cves/CVE-2026-99065","pt":"https://www.redsauce.net/pt/cves/CVE-2026-99065","de":"https://www.redsauce.net/de/cves/CVE-2026-99065","sk":"https://www.redsauce.net/sk/cves/CVE-2026-99065","el":"https://www.redsauce.net/el/cves/CVE-2026-99065"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-99065"}}