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Linux KernelOperating system · Linux

CVE-2026-43402

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-08
Fix available
A fix is available. Upgrade to 6.18.19 / 6.19.9 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A use-after-free vulnerability in the Linux kernel's kthread subsystem allows memory corruption when kthreads exit via make_task_dead(). The bug occurs because struct pid (144 bytes) and struct kthread (144 bytes) share the same slab cache, and when a kthread exits without going through kthread_exit(), the affinity_node cleanup is missed. This leaves dangling pointers in the global kthread_affinity_list that get corrupted by subsequent list_del() operations, corrupting the pid's rcu.func pointer.

MitigationApply the kernel patch that consolidates all kthread exit paths by making kthread_exit() a macro calling do_exit() and adding kthread_do_exit() called from do_exit() for PF_KTHREAD tasks. This ensures kthread-specific cleanup always occurs regardless of exit path.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.14, < 6.18.19>= 6.19, < 6.19.9= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify running kernel version
    Run 'uname -r' or 'cat /proc/version' to get the exact kernel version string
    Affected if The version falls within >= 6.14, < 6.18.19; >= 6.19, < 6.19.9; or = 7.0
  2. Verify kthread affinity list support exists
    Check if /sys/kernel/debug/sched/kthread_affinity exists or look for CONFIG_KTHREAD_AFFINITY in kernel config via 'cat /boot/config-$(uname -r)' or 'zcat /proc/config.gz' if available
    Affected if The kernel has kthread affinity support enabled (CONFIG_KTHREAD_AFFINITY=y or =m)
  3. Check for active kthreads with CPU affinity
    List kthreads with affinity set by examining /sys/kernel/debug/sched/kthread_affinity if it exists, or check 'ps -o pid,comm,psr' for kthreads with specific CPU bindings
    Affected if There are kthreads with non-default CPU affinity masks (bound to specific CPUs rather than -1 for all CPUs)
  4. Inspect kthread exit code paths
    Check if the running kernel has the patched exit path by examining /proc/kallsyms for symbols 'kthread_exit' and 'do_exit', or analyze the kernel source if accessible
    Affected if The kernel is still using the vulnerable make_task_dead() bypass path without the consolidated do_exit() or kthread_do_exit() implementation

You are affected if your kernel version is in the vulnerable range AND kthreads with CPU affinity are in use on the system, allowing the dangling pointer scenario in kthread_affinity_list to trigger.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.18.19 / 6.19.9 or later
Fixed in 6.18.196.19.9
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that consolidates all kthread exit paths by making kthread_exit() a macro calling do_exit() and adding kthread_do_exit() called from do_exit() for PF_KTHREAD tasks. This ensures kthread-specific cleanup always occurs regardless of exit path.

Recommended fix High confidence

6.18.19 or later for 6.14-6.18.x branches; 6.19.9 or later for 6.19.x branch; 7.1 or later for 7.0

  1. Identify the currently running kernel version using `uname -r`
  2. If running kernel >= 6.14 and < 6.18.19: plan upgrade to kernel version 6.18.19 or later
  3. If running kernel >= 6.19 and < 6.19.9: plan upgrade to kernel version 6.19.9 or later
  4. If running kernel 7.0: wait for 7.1 stable release and upgrade then
  5. Apply the upgrade through your distribution's package manager (e.g., `apt-get dist-upgrade`, `yum update`, or `dnf upgrade`)
  6. Reboot the system into the new kernel
  7. Verify the kernel version after reboot with `uname -r` to confirm the fix is applied
  8. Alternatively, if immediate patching is required, cherry-pick commit 28aaa9c39945b7925a1cc1d513c8f21ed38f5e4f from kernel.org and rebuild the kernel
Caveat Kernel upgrades may require matching system utilities and drivers; some hardware may need firmware updates; ensure compatibility with critical system components before upgrading production systems

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing16.0 h
  • Review / QA8.0 h
42.0 hours of engineering $7,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43402 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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