Cloudanix VulnDB

CVE-2026-23167

Medium · 4.7

CVSS

4.7

EPSS

0.1%

Published

Feb 14, 2026

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A flaw in how the Linux kernel handles wireless device shutdown can cause crashes on some systems when certain power or radio controls are used.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
High
Impact
Denial Of Service
Component
OS kernel
Class
Race Condition
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

Race condition in nci_unregister_device allows rfkill-triggered nci_close_device to operate after cmd_wq destruction, triggering lockdep warnings and potential use-after-free or kernel instability during NFC device teardown.

Why it matters to the business

Systems using NFC on affected Linux kernels may experience crashes or denial of service when rfkill interacts with device removal, affecting availability of wireless functionality on Ubuntu Pro 18.04 AWS instances until patched.

How an attack unfolds

A local attacker triggers device close via virtual_ncidev while rfkill operations run concurrently, exploiting the ordering where cmd_wq is destroyed before rfkill unregistration completes, leading to invalid workqueue access.

How to fix it

Upgrade linux-aws-5.4 packages to version 5.4.0-1109.118~18.04.1 or later on Ubuntu Pro 18.04 LTS systems; reboot after installation to load the corrected kernel.

How to confirm the fix worked

Verify installed kernel version matches or exceeds 5.4.0-1109.118~18.04.1, confirm absence of the race in nci_unregister_device source, and test rfkill operations with NFC device close sequences under load.

Typical attack path

  1. Obtain local user access on affected kernel
  2. Open virtual_ncidev file descriptor
  3. Trigger concurrent rfkill block operation
  4. Close the NFC device file descriptor to invoke nci_unregister_device
  5. Observe resulting lockdep splat or kernel fault during nci_close_device

How to detect it

Search kernel logs for DEBUG_LOCKS_WARN_ON messages referencing hlock_class or __lock_acquire during nci_close_device or rfkill_set_block calls; examine dmesg or journalctl for workqueue and NFC NCI stack traces post-device close events.

What your security team should do

  • Prioritize patching Ubuntu Pro 18.04 AWS instances running linux-aws-5.4 within standard maintenance windows
  • Monitor for kernel oops or lockdep warnings involving nci_close_device and rfkill
  • Restrict local NFC device access via AppArmor or SELinux policies where feasible
  • Review downstream package dependencies for any additional NFC-related kernels requiring updates

The record

In the Linux kernel, the following vulnerability has been resolved: nfc: nci: Fix race between rfkill and nci_unregister_device(). syzbot reported the splat below [0] without a repro. It indicates that struct nci_dev.cmd_wq had been destroyed before nci_close_device() was called via rfkill. nci_dev.cmd_wq is only destroyed in nci_unregister_device(), which (I think) was called from virtual_ncidev_close() when syzbot close()d an fd of virtual_ncidev. The problem is that nci_unregister_device() destroys nci_dev.cmd_wq first and then calls nfc_unregister_device(), which removes the device from rfkill by rfkill_unregister(). So, the device is still visible via rfkill even after nci_dev.cmd_wq is destroyed. Let's unregister the device from rfkill first in nci_unregister_device(). Note that we cannot call nfc_unregister_device() before nci_close_device() because 1) nfc_unregister_device() calls device_del() which frees all memory allocated by devm_kzalloc() and linked to ndev->conn_info_list 2) nci_rx_work() could try to queue nci_conn_info to ndev->conn_info_list which could be leaked Thus, nfc_unregister_device() is split into two functions so we can remove rfkill interfaces only before nci_close_device(). [0]: DEBUG_LOCKS_WARN_ON(1) WARNING: kernel/locking/lockdep.c:238 at hlock_class kernel/locking/lockdep.c:238 [inline], CPU#0: syz.0.8675/6349 WARNING: kernel/locking/lockdep.c:238 at check_wait_context kernel/locking/lockdep.c:4854 [inline], CPU#0: syz.0.8675/6349 WARNING: kernel/locking/lockdep.c:238 at __lock_acquire+0x39d/0x2cf0 kernel/locking/lockdep.c:5187, CPU#0: syz.0.8675/6349 Modules linked in: CPU: 0 UID: 0 PID: 6349 Comm: syz.0.8675 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 RIP: 0010:hlock_class kernel/locking/lockdep.c:238 [inline] RIP: 0010:check_wait_context kernel/locking/lockdep.c:4854 [inline] RIP: 0010:__lock_acquire+0x3a4/0x2cf0 kernel/locking/lockdep.c:5187 Code: 18 00 4c 8b 74 24 08 75 27 90 e8 17 f2 fc 02 85 c0 74 1c 83 3d 50 e0 4e 0e 00 75 13 48 8d 3d 43 f7 51 0e 48 c7 c6 8b 3a de 8d <67> 48 0f b9 3a 90 31 c0 0f b6 98 c4 00 00 00 41 8b 45 20 25 ff 1f RSP: 0018:ffffc9000c767680 EFLAGS: 00010046 RAX: 0000000000000001 RBX: 0000000000040000 RCX: 0000000000080000 RDX: ffffc90013080000 RSI: ffffffff8dde3a8b RDI: ffffffff8ff24ca0 RBP: 0000000000000003 R08: ffffffff8fef35a3 R09: 1ffffffff1fde6b4 R10: dffffc0000000000 R11: fffffbfff1fde6b5 R12: 00000000000012a2 R13: ffff888030338ba8 R14: ffff888030338000 R15: ffff888030338b30 FS: 00007fa5995f66c0(0000) GS:ffff8881256f8000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7e72f842d0 CR3: 00000000485a0000 CR4: 00000000003526f0 Call Trace: <TASK> lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:3940 __flush_workqueue+0x14b/0x14f0 kernel/workqueue.c:3982 nci_close_device+0x302/0x630 net/nfc/nci/core.c:567 nci_dev_down+0x3b/0x50 net/nfc/nci/core.c:639 nfc_dev_down+0x152/0x290 net/nfc/core.c:161 nfc_rfkill_set_block+0x2d/0x100 net/nfc/core.c:179 rfkill_set_block+0x1d2/0x440 net/rfkill/core.c:346 rfkill_fop_write+0x461/0x5a0 net/rfkill/core.c:1301 vfs_write+0x29a/0xb90 fs/read_write.c:684 ksys_write+0x150/0x270 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa59b39acb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa5995f6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fa59b615fa0 RCX: 00007fa59b39acb9 RDX: 0000000000000008 RSI: 0000200000000080 RDI: 0000000000000007 RBP: 00007fa59b408bf7 R08: ---truncated---

Affected packages

Ecosystem Package Introduced Fixed
Linux Kernel 3.2.0 5.10.249
openSUSE:Leap 16.0 dtb-aarch64 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-64kb 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-azure 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-default 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-default-base 0 6.12.0-160000.27.1.160000.2.8
openSUSE:Leap 16.0 kernel-docs 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-kvmsmall 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-obs-build 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-obs-qa 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-rt 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-source 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-syms 0 6.12.0-160000.27.1
openSUSE:Leap 16.0 kernel-zfcpdump 0 6.12.0-160000.27.1

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