{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-43402", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-05-01T14:12:56.007Z", "datePublished": "2026-05-08T14:21:43.550Z", "dateUpdated": "2026-08-05T12:27:46.142Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:27:46.142Z" }, "descriptions": [ { "lang": "en", "value": "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 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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - In the most severe reasonable deployment, network-facing in-kernel services such as ksmbd create kthreads and process unauthenticated remote traffic in those kthreads. The vulnerable kthread lifecycle and exit cleanup can therefore be reached from a remote network path.\nAC:L - The bug is a deterministic cleanup omission once an affected kthread exits through a bypass path such as make_task_dead/do_exit, and the resulting dangling list entry can be exercised by normal kthread churn. There is no attacker-uncontrolled race required for the UAF mechanism itself.\nPR:N - For network-facing kthread users such as ksmbd connection handlers, an unauthenticated remote peer can drive pre-authentication packet handling and connection-thread creation. No local account or kernel capability is required in that scenario.\nUI:N - Exploitation does not require a victim user to open a file, mount a filesystem, or perform another interactive action. The attacker can send traffic or otherwise drive the reachable service path directly.\nS:U - The corruption occurs within the Linux kernel and impacts kernel-managed memory and control flow. It does not inherently cross a separate security authority such as a VM-to-host or IOMMU boundary.\nC:H - This is a use-after-free of a freed struct kthread left linked into a global list, with later list operations writing into reused slab memory such as struct pid. Kernel UAF memory corruption is treated as capable of yielding high confidentiality impact through read/info-disclosure primitives.\nI:H - The stale list entry causes writes through dangling list pointers into a reused object, including corruption of sensitive fields such as an RCU callback pointer. Such kernel UAF corruption is defensibly exploitable for arbitrary write or control-flow hijack.\nA:H - The observed failure mode is corrupted RCU callback function pointers and kernel crashes. Even without full exploitation, repeated triggering can oops or panic the kernel, causing high availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/kthread.h", "kernel/exit.c", "kernel/kthread.c" ], "versions": [ { "version": "4d13f4304fa43471bfea101658a11feec7b28ac0", "lessThan": "4729c7b00a347fd37d0cbc265b85f2884c3e06b6", "status": "affected", "versionType": "git" }, { "version": "4d13f4304fa43471bfea101658a11feec7b28ac0", "lessThan": "5a591d7a5e48d30100943940a30a6ab41b15c672", "status": "affected", "versionType": "git" }, { "version": "4d13f4304fa43471bfea101658a11feec7b28ac0", "lessThan": "28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/kthread.h", "kernel/exit.c", "kernel/kthread.c" ], "versions": [ { "version": "6.14", "status": "affected" }, { "version": "0", "lessThan": "6.14", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.19", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.9", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.18.19" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.19.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "7.0" } ] } ] } ], "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" } ], "title": "kthread: consolidate kthread exit paths to prevent use-after-free", "x_generator": { "engine": "bippy-1.2.0" } } } }