{"id":"CVE-2026-99065","title":"cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()\n\nWith commit 2125c0034c5d (\"cgroup/cpuset: Make cpuset hotplug processing\nsynchronous\"), the cpuset ho…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < 8d88d3221204fbb1b6dc2c0f2f2181fe49126639","Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < a21c255159bfe0034740292e10d2e258feeeb10d","Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < 23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2","Linux 6.16"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:23:08.458Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99065","references":[{"url":"https://git.kernel.org/stable/c/8d88d3221204fbb1b6dc2c0f2f2181fe49126639"},{"url":"https://git.kernel.org/stable/c/a21c255159bfe0034740292e10d2e258feeeb10d"},{"url":"https://git.kernel.org/stable/c/23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.518Z","slug":"CVE-2026-99065","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()\n\nWith commit 2125c0034c5d (\"cgroup/cpuset: Make cpuset hotplug processing\nsynchronous\"), the cpuset hotplug operation becomes synchronous. That\ncommit also removes the code that handles race between cpuset_hotplug_work\nand cpu hotplug notifier with the assumption that race is now gone.\nLater commit 7a0aabd9ce69 (\"cgroup/cpuset: Always use cpu_active_mask\")\nupdates the cpuset code to always use cpu_active_mask instead of\ncpu_online_mask in some places including guarantee_online_cpus() which\nis renamed to guarantee_active_cpus() in that commit.\n\nIn the case of CPU offline operation, cpu_active_mask is updated\nfirst in sched_cpu_deactivate() to remove the offline CPU before\ncpuset_handle_hotplug() is called to update the effective_cpus of the\naffected cpusets. The cpu_online_mask is updated after that near the end\nof the offline operation to remove the offline CPU. As a result, the race\ncomes back and the top cpuset may not have any active CPU leading to NULL\npointer dereference during the race window when guarantee_active_cpus()\nis called after cpu_active_mask is updated to remove the CPU to be torn\ndown but before cpuset_handle_hotplug() is able to properly update the\neffective_cpus of the top cpuset.\n\nFix this by adding back the NULL cs check to avoid this problem.\n\n## Affected\n\n- `Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < 8d88d3221204fbb1b6dc2c0f2f2181fe49126639`\n- `Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < a21c255159bfe0034740292e10d2e258feeeb10d`\n- `Linux >= 7a0aabd9ce697fc581ec691b21f748050fbcf004 < 23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2`\n- `Linux 6.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}