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CVE-2026-72016— cpu/hotplug: Fix NULL kobject warning in cpuhp_smt_enable()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.15版本存在安全漏洞，该漏洞源于在cpuhp_smt_enable()中，当arm64启动时maxcpus大于实际present CPU数时，对未注册的CPU调用_cpu_up()导致sysfs_create_group()使用NULL kobject，可能触发内核警告。

AI Predicted 3.3 Difficulty: Theoretical EPSS 0.20% · P10

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb< ccdf1770a4ba27e31599d24ad970d77a371c7912 affected
eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb< 901a489d89ee9c854624c8444090e38e70aed234 affected
eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb< f9a82544c7174851f5c7524622f5966dcafd3a47 affected
6.15 affected
< 6.15 unaffected
6.18.40≤ 6.18.* unaffected
7.1.5≤ 7.1.* unaffected
7.2≤ * unaffected
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I. Basic Information for CVE-2026-72016

Vulnerability Information
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Vulnerability Title
cpu/hotplug: Fix NULL kobject warning in cpuhp_smt_enable()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: cpu/hotplug: Fix NULL kobject warning in cpuhp_smt_enable() On arm64, when booting with `maxcpus` greater than the number of present CPUs (e.g., QEMU -smp cpus=4,maxcpus=8), some CPUs are marked as 'present' but have not yet been registered via register_cpu(). Consequently, the per-cpu device objects for these CPUs are not yet initialized. In cpuhp_smt_enable(), the code iterates over all present CPUs. Calling _cpu_up() for these unregistered CPUs eventually leads to sysfs_create_group() being called with a NULL kobject (or a kobject without a directory), triggering the following warning in fs/sysfs/group.c: WARNING: fs/sysfs/group.c:137 at internal_create_group+0x41c/0x4bc, CPU#2: sh/181 [...] Call trace: internal_create_group+0x41c/0x4bc (P) sysfs_create_group+0x18/0x24 topology_add_dev+0x1c/0x28 cpuhp_invoke_callback+0x104/0x20c __cpuhp_invoke_callback_range+0x94/0x11c _cpu_up+0x200/0x37c When booting with ACPI, arm64 smp_prepare_cpus() currently sets all enumerated CPUs as "present" regardless of their status in the MADT. This causes issues with SMT hotplug control. For instance, with QEMU's "-smp 4,maxcpus=8" configuration, the MADT GICC entries are populated as follows: 1. The first four CPUs: `Enabled` set but `Online Capable` not set. 2. The remaining four CPUs: `Online Capable` set but `Enabled` not set to support potential hot-plugging. Fix this by: 1. When booting with ACPI, checking the ACPI_MADT_ENABLED flag in the GICC entry before calling set_cpu_present() during SMP initialization. 2. Properly managing the present mask in acpi_map_cpu() and acpi_unmap_cpu() to support actual CPU hotplug events, This aligns with other architectures like x86 and LoongArch. 3. Update the arm64 CPU hotplug documentation to no longer state that all online-capable vCPUs are marked as present by the kernel at boot time. This ensures that only physically available or explicitly enabled CPUs are in the present mask, keeping the SMT control logic consistent with the actual hardware state.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.15版本存在安全漏洞，该漏洞源于在cpuhp_smt_enable()中，当arm64启动时maxcpus大于实际present CPU数时，对未注册的CPU调用_cpu_up()导致sysfs_create_group()使用NULL kobject，可能触发内核警告。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb ~ ccdf1770a4ba27e31599d24ad970d77a371c7912 -
Linux Linux 6.15 -

II. Public POCs for CVE-2026-72016

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III. Intelligence Information for CVE-2026-72016

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Patches & Fixes for CVE-2026-72016 (3)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72217 9.8 CRITICAL SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing
CVE-2026-72491 9.8 CRITICAL net/9p: fix race condition on rdma->state in trans_rdma.c
CVE-2026-72221 9.8 CRITICAL sunrpc: wait for in-flight TLS handshake callback when cancel loses race
CVE-2026-72222 9.8 CRITICAL sunrpc: pin svc_xprt across the asynchronous TLS handshake callback
CVE-2026-72220 9.8 CRITICAL sunrpc: harden rq_procinfo lifecycle to prevent double-free
CVE-2026-72398 9.8 CRITICAL sctp: add INIT verification after cookie unpacking
CVE-2026-72477 9.8 CRITICAL fs/ntfs3: call _ntfs_bad_inode() when failing to rename
CVE-2026-72466 9.8 CRITICAL xprtrdma: Fix bcall rep leak and unbounded peek
CVE-2026-72472 9.8 CRITICAL nfs: use nfsi->rwsem to protect traversal of the file lock list
CVE-2026-72473 9.8 CRITICAL xprtrdma: Decouple req recycling from RPC completion
CVE-2026-72399 9.8 CRITICAL net: enetc: check the number of BDs needed for xdp_frame
CVE-2026-74398 9.8 CRITICAL ipv6: addrconf: bail out of dad_failure when state is no longer POSTDAD

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-72016

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