Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 19999.44.21

medium Tenable Cloud Security Plugin ID 470038

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

- 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. (CVE-2026-72016)

Solution

Update the sys-kernel/cchost-kernel-6_18 library and its related packages to version 19999.44.21 or later.

Plugin Details

Severity: Medium

ID: 470038

Version: Revision 1.6

Type: Local

Family: Google COS Security Checks

Published: 10/3/2026

Updated: 10/6/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.67

Vendor

Vendor Severity: LOW

CVSS v2

Risk Factor: Medium

Base Score: 4.7

Temporal Score: 3.5

Vector: CVSS2#AV:L/AC:M/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2026-72016

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 8/15/2026

Reference Information

CVE: CVE-2026-72016

Detections

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