Linux Kernel up to 6.18.39/7.1.4/7.2-rc2 cpu/hotplug fs/sysfs/group.c cpuhp_smt_enable initialization

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CTI Interest Score
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4.7$0-$5k0.47

Summaryinfo

A vulnerability classified as problematic was found in Linux Kernel up to 6.18.39/7.1.4/7.2-rc2. Affected by this issue is the function cpuhp_smt_enable of the file fs/sysfs/group.c of the component cpu/hotplug. Such manipulation leads to initialization. This vulnerability is documented as CVE-2026-72016. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.39/7.1.4/7.2-rc2. It has been rated as problematic. Affected by this issue is the function cpuhp_smt_enable of the file fs/sysfs/group.c of the component cpu/hotplug. The manipulation with an unknown input leads to a initialization vulnerability. Using CWE to declare the problem leads to CWE-665. The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. Impacted is availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-72016 since 08/09/2026. The exploitation is known to be easy. The attack may be launched remotely. The exploitation needs additional levels of successful authentication. Technical details are known, but there is no available exploit.

Upgrading to version 6.18.40, 7.1.5 or 7.2-rc3 eliminates this vulnerability. Applying the patch ccdf1770a4ba27e31599d24ad970d77a371c7912/901a489d89ee9c854624c8444090e38e70aed234/f9a82544c7174851f5c7524622f5966dcafd3a47 is able to eliminate this problem.

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Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.9
VulDB Meta Temp Score: 4.7

VulDB Base Score: 4.9
VulDB Temp Score: 4.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Initialization
CWE: CWE-665
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.40/7.1.5/7.2-rc3
Patch: ccdf1770a4ba27e31599d24ad970d77a371c7912/901a489d89ee9c854624c8444090e38e70aed234/f9a82544c7174851f5c7524622f5966dcafd3a47

Timelineinfo

08/09/2026 CVE reserved
08/15/2026 +6 days Advisory disclosed
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-72016 (🔒)
GCVE (CVE): GCVE-0-2026-72016
GCVE (VulDB): GCVE-100-390446

Entryinfo

Created: 08/15/2026 11:26
Changes: 08/15/2026 11:26 (60)
Complete: 🔍
Cache ID: 216::103

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