CVE-2026-72016
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:
Leer descripción completaMostrar menos
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.
Fix this by:
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.
Detalles técnicos trazas, registros y código del informe original
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
2. The remaining four CPUs: `Online Capable` set but `Enabled` not set
to support potential hot-plugging.
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.CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 3/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-72016",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb",
"lessThan": "ccdf1770a4ba27e31599d24ad970d77a371c7912",
"versionType": "git"
},
{
"status": "affected",
"version": "eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb",
"lessThan": "901a489d89ee9c854624c8444090e38e70aed234",
"versionType": "git"
},
{
"status": "affected",
"version": "eed4583bcf9a60f8d6dd3a3c7c94dea28134b1eb",
"lessThan": "f9a82544c7174851f5c7524622f5966dcafd3a47",
"versionType": "git"
}
],
"programFiles": [
"Documentation/arch/arm64/cpu-hotplug.rst",
"arch/arm64/kernel/acpi.c",
"arch/arm64/kernel/smp.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"Documentation/arch/arm64/cpu-hotplug.rst",
"arch/arm64/kernel/acpi.c",
"arch/arm64/kernel/smp.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T06:21:00.433",
"references": [
{
"url": "https://git.kernel.org/stable/c/901a489d89ee9c854624c8444090e38e70aed234",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ccdf1770a4ba27e31599d24ad970d77a371c7912",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f9a82544c7174851f5c7524622f5966dcafd3a47",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncpu/hotplug: Fix NULL kobject warning in cpuhp_smt_enable()\n\nOn arm64, when booting with `maxcpus` greater than the number of present\nCPUs (e.g., QEMU -smp cpus=4,maxcpus=8), some CPUs are marked as 'present'\nbut have not yet been registered via register_cpu(). Consequently,\nthe per-cpu device objects for these CPUs are not yet initialized.\n\nIn cpuhp_smt_enable(), the code iterates over all present CPUs. Calling\n_cpu_up() for these unregistered CPUs eventually leads to\nsysfs_create_group() being called with a NULL kobject (or a kobject\nwithout a directory), triggering the following warning in\nfs/sysfs/group.c:\n\n WARNING: fs/sysfs/group.c:137 at internal_create_group+0x41c/0x4bc, CPU#2: sh/181\n [...]\n Call trace:\n internal_create_group+0x41c/0x4bc (P)\n sysfs_create_group+0x18/0x24\n topology_add_dev+0x1c/0x28\n cpuhp_invoke_callback+0x104/0x20c\n __cpuhp_invoke_callback_range+0x94/0x11c\n _cpu_up+0x200/0x37c\n\nWhen booting with ACPI, arm64 smp_prepare_cpus() currently sets all\nenumerated CPUs as \"present\" regardless of their status in the MADT. This\ncauses issues with SMT hotplug control. For instance, with QEMU's\n\"-smp 4,maxcpus=8\" configuration, the MADT GICC entries are populated as\nfollows:\n\n1. The first four CPUs: `Enabled` set but `Online Capable` not set.\n\n2. The remaining four CPUs: `Online Capable` set but `Enabled` not set\n to support potential hot-plugging.\n\nFix this by:\n\n1. When booting with ACPI, checking the ACPI_MADT_ENABLED flag in the GICC\n entry before calling set_cpu_present() during SMP initialization.\n\n2. Properly managing the present mask in acpi_map_cpu() and\n acpi_unmap_cpu() to support actual CPU hotplug events, This aligns with\n other architectures like x86 and LoongArch.\n\n3. Update the arm64 CPU hotplug documentation to no longer state that all\n online-capable vCPUs are marked as present by the kernel at boot time.\n\nThis ensures that only physically available or explicitly enabled CPUs\nare in the present mask, keeping the SMT control logic consistent with\nthe actual hardware state."
}
],
"lastModified": "2026-08-17T06:17:59.117",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}