CVE-2026-64512
Received Received - Intake

UBSAN Shift-Out-of-Bounds in Linux Kernel ACPI CPPC

Publication date: 2026-07-25

Last updated on: 2026-07-25

Assigner: kernel.org

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_PLATFORM_COMM, drop the code correcting the size.

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Meta Information

Published
2026-07-25
Last Modified
2026-07-25
Generated
2026-08-14
AI Q&A
2026-07-25
EPSS Evaluated
2026-08-13
NVD
CVE-2026-64512
EUVD
EUVD-2026-48856

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 7.0.10-201.fc44.aarch64

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a misuse of the ACPI CPPC (Collaborative Processor Performance Control) field. The issue occurs when the reg->access_width value is misinterpreted based on reg->space_id type, particularly for ACPI_ADR_SPACE_PLATFORM_COMM which uses access_width to indicate the PCC region. This can lead to a UBSAN (Undefined Behavior Sanitizer) warning due to a shift-out-of-bounds error when the value exceeds 4.

Detection Guidance

This vulnerability is specific to the Linux kernel and relates to ACPI CPPC functionality. Detection requires checking kernel logs for UBSAN warnings related to shift-out-of-bounds errors in drivers/acpi/cppc_acpi.c. Monitor system logs for messages indicating 'shift-out-of-bounds' or 'ubsan_epilogue' with references to cppc_write or cppc_set_perf.

Impact Analysis

This vulnerability may cause system instability or crashes due to undefined behavior in the kernel. It could lead to unexpected errors during CPU performance control operations, potentially affecting system performance or causing kernel panics. Systems using affected Linux kernel versions may experience issues with ACPI CPPC functionality.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a low-level kernel issue causing a UBSAN warning due to incorrect handling of ACPI CPPC register access width, which could lead to undefined behavior in rare cases. No data exposure or privacy impact is indicated.

Mitigation Strategies

Update to a patched Linux kernel version that includes the fix for this issue. The vulnerability is resolved by validating region types and access_width values in ACPI CPPC handling. Check your distribution's security advisories for kernel updates addressing CVE-2026-64512.

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