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VulnerabilityPublished Updated

CVE-2026-43402: Linux kernel · kthread: consolidate kthread exit paths to prevent use-after-free

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in 4729c7b00a347fd37d0cbc265b85f2884c3e06b6 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 46% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in 4729c7b00a347fd37d0cbc265b85f2884c3e06b6, 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f, 5a591d7a5e48d30100943940a30a6ab41b15c672
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade Linux kernel to 4729c7b00a347fd37d0cbc265b85f2884c3e06b6, 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f or 5a591d7a5e48d30100943940a30a6ab41b15c672.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 4d13f4304fa43471bfea101658a11feec7b28ac0, < 4729c7b00a347fd37d0cbc265b85f2884c3e06b6
Fixed in
  • 4729c7b00a347fd37d0cbc265b85f2884c3e06b6
LinuxLinuxAffected
  • ≥ 4d13f4304fa43471bfea101658a11feec7b28ac0, < 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f
Fixed in
  • 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f
LinuxLinuxAffected
  • ≥ 4d13f4304fa43471bfea101658a11feec7b28ac0, < 5a591d7a5e48d30100943940a30a6ab41b15c672
Fixed in
  • 5a591d7a5e48d30100943940a30a6ab41b15c672
LinuxLinuxAffected
  • =6.14
Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: kthread: consolidate kthread exit paths to prevent use-after-free Guillaume reported crashes via corrupted RCU callback function pointers during KUnit testing. The crash was traced back to the pidfs rhashtable conversion which replaced the 24-byte rb_node with an 8-byte rhash_head in struct pid, shrinking it from 160 to 144 bytes. struct kthread (without CONFIG_BLK_CGROUP) is also 144 bytes. With CONFIG_SLAB_MERGE_DEFAULT and SLAB_HWCACHE_ALIGN both round up to 192 bytes and share the same slab cache. struct pid.rcu.func and struct kthread.affinity_node both sit at offset 0x78. When a kthread exits via make_task_dead() it bypasses kthread_exit() and misses the affinity_node cleanup. free_kthread_struct() frees the memory while the node is still linked into the global kthread_affinity_list. A subsequent list_del() by another kthread writes through dangling list pointers into the freed and reused memory, corrupting the pid's rcu.func pointer. Instead of patching free_kthread_struct() to handle the missed cleanup, consolidate all kthread exit paths. Turn kthread_exit() into a macro that calls do_exit() and add kthread_do_exit() which is called from do_exit() for any task with PF_KTHREAD set. This guarantees that kthread-specific cleanup always happens regardless of the exit path - make_task_dead(), direct do_exit(), or kthread_exit(). Replace __to_kthread() with a new tsk_is_kthread() accessor in the public header. Export do_exit() since module code using the kthread_exit() macro now needs it directly.

References

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