{"id":"CVE-2026-43402","title":"kthread: consolidate kthread exit paths to prevent use-after-free","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nkthread: consolidate kthread exit paths to prevent use-after-free\n\nGuillaume reported crashes via corrupted RCU callback function pointers\nduring KUnit testing. The cra…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 4729c7b00a347fd37d0cbc265b85f2884c3e06b6","Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 5a591d7a5e48d30100943940a30a6ab41b15c672","Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f","Linux 6.14"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T15:17:02.801558Z"},"published":"2026-05-08","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:20:40.794Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-43402","references":[{"url":"https://git.kernel.org/stable/c/4729c7b00a347fd37d0cbc265b85f2884c3e06b6"},{"url":"https://git.kernel.org/stable/c/5a591d7a5e48d30100943940a30a6ab41b15c672"},{"url":"https://git.kernel.org/stable/c/28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f"}],"tags":["cve.org"],"epss":0.0067,"epssPercentile":0.50977,"ingestedAt":"2026-10-16T17:24:46.695Z","slug":"CVE-2026-43402","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nkthread: consolidate kthread exit paths to prevent use-after-free\n\nGuillaume reported crashes via corrupted RCU callback function pointers\nduring KUnit testing. The crash was traced back to the pidfs rhashtable\nconversion which replaced the 24-byte rb_node with an 8-byte rhash_head\nin struct pid, shrinking it from 160 to 144 bytes.\n\nstruct kthread (without CONFIG_BLK_CGROUP) is also 144 bytes. With\nCONFIG_SLAB_MERGE_DEFAULT and SLAB_HWCACHE_ALIGN both round up to\n192 bytes and share the same slab cache. struct pid.rcu.func and\nstruct kthread.affinity_node both sit at offset 0x78.\n\nWhen a kthread exits via make_task_dead() it bypasses kthread_exit() and\nmisses the affinity_node cleanup. free_kthread_struct() frees the memory\nwhile the node is still linked into the global kthread_affinity_list. A\nsubsequent list_del() by another kthread writes through dangling list\npointers into the freed and reused memory, corrupting the pid's\nrcu.func pointer.\n\nInstead of patching free_kthread_struct() to handle the missed cleanup,\nconsolidate all kthread exit paths. Turn kthread_exit() into a macro\nthat calls do_exit() and add kthread_do_exit() which is called from\ndo_exit() for any task with PF_KTHREAD set. This guarantees that\nkthread-specific cleanup always happens regardless of the exit path -\nmake_task_dead(), direct do_exit(), or kthread_exit().\n\nReplace __to_kthread() with a new tsk_is_kthread() accessor in the\npublic header. Export do_exit() since module code using the\nkthread_exit() macro now needs it directly.\n\n## Affected\n\n- `Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 4729c7b00a347fd37d0cbc265b85f2884c3e06b6`\n- `Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 5a591d7a5e48d30100943940a30a6ab41b15c672`\n- `Linux >= 4d13f4304fa43471bfea101658a11feec7b28ac0 < 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f`\n- `Linux 6.14`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}