CVE-2026-64512

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ACPI: CPPC: Suppress UBSAN warning caused by field misuse

The definition of reg->access_width changes depending on the

reg->space_id type. Type ACPI_ADR_SPACE_PLATFORM_COMM uses

access_width to indicate the PCC region, which can result in a UBSAN

if the value is greater than 4.

For example:

UBSAN: shift-out-of-bounds in drivers/acpi/cppc_acpi.c:1090:9

shift exponent 32 is too large for 32-bit type 'int'

CPU: 61 UID: 0 PID: 1220 Comm: (udev-worker) Not tainted 7.0.10-201.fc44.aarch64 #1 PREEMPT(lazy)

Hardware name: To be filled by O.E.M.

Call trace:

...(trimming)

ubsan_epilogue+0x10/0x48

__ubsan_handle_shift_out_of_bounds+0xdc/0x1e0

cpc_write+0x4d0/0x670

cppc_set_perf+0x18c/0x490

cppc_cpufreq_cpu_init+0x1c8/0x380 [cppc_cpufreq]

... (trimming)

Lets fix this by validating the region type, as well as whether

access_width has a value. Then since we are returning bit_width

directly for ACPI_ADR_SPACE

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References