CVE-2026-98537
Received Received - Intake

NULL dereference in Linux kernel workqueue subsystem

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: workqueue: Fix NULL current_pwq deref in flush dependency check check_flush_dependency() uses current_wq_worker() to determine whether the caller is a workqueue worker and then dereferences worker->current_pwq to test whether the current workqueue is WQ_MEM_RECLAIM. current_wq_worker() only means that %current has PF_WQ_WORKER set. A kworker can reach check_flush_dependency() while it is not executing a work item. One such path is worker_thread() acting as the pool manager, where create_worker() does GFP_KERNEL allocation and the allocation path invokes the OOM notifier. In that state worker->current_pwq is NULL because current_pwq is set only by process_one_work() and cleared again after the work function returns. [ 416.760634][ T375] Call trace: [ 416.760638][ T375] check_flush_dependency+0x80/0x120 (P) [ 416.760648][ T375] __flush_work+0x98/0x224 [ 416.760657][ T375] flush_work+0x30/0x44 [ 416.760665][ T375] ... [ 416.760710][ T375] blocking_notifier_call_chain+0x58/0xa0 [ 416.760719][ T375] out_of_memory+0xb4/0x458 [ 416.760730][ T375] __alloc_pages_may_oom+0x11c/0x1a8 [ 416.760739][ T375] __alloc_pages_slowpath+0x314/0x46c [ 416.760746][ T375] __alloc_frozen_pages_noprof+0x110/0x1a4 [ 416.760753][ T375] new_slab+0x12c/0x484 [ 416.760759][ T375] ___slab_alloc+0x7a8/0xc7c [ 416.760765][ T375] __slab_alloc+0x74/0xd8 [ 416.760772][ T375] __kmalloc_cache_node_noprof+0x2ac/0x304 [ 416.760779][ T375] alloc_worker+0x28/0x60 [ 416.760785][ T375] create_worker+0x4c/0x20c [ 416.760790][ T375] worker_thread+0xe8/0x2b8 [ 416.760796][ T375] kthread+0x1a8/0x200 [ 416.760805][ T375] ret_from_fork+0x10/0x20 Guard the WQ_MEM_RECLAIM-worker warning with worker->current_pwq. If the kworker is not currently executing a work item, there is no current workqueue to diagnose with that warning. The PF_MEMALLOC warning is left unchanged so explicit reclaim context flushing a !WQ_MEM_RECLAIM target is still reported.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98537
EUVD
EUVD-2026-103582

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux fca839c00a12d682cb59b3b620d109a1d850b262
Linux Linux 4.5

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Exploitability

CWE
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability where a NULL pointer dereference flaw exists in the workqueue subsystem. The issue occurs in check_flush_dependency() when it incorrectly assumes a workqueue worker is executing a work item, leading to a crash when worker->current_pwq is NULL. This happens during OOM notifier invocation in worker_thread() while managing the pool.

Detection Guidance

This vulnerability is specific to the Linux kernel and may not have direct network detection methods. Monitor kernel logs for NULL pointer dereference errors in workqueue functions or OOM-related crashes. Check for kernel panics or system hangs during memory allocation or workqueue operations.

Impact Analysis

This vulnerability can cause system crashes or instability in Linux systems using affected kernel versions. It may lead to kernel panics or unexpected reboots, potentially disrupting services and causing data loss.

Mitigation Strategies

Apply the latest Linux kernel patches that address this issue. Update your system to a kernel version that includes the fix for CVE-2026-98537. Monitor kernel.org or your distribution's security advisories for updates.

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