In the Linux kernel, the following vulnerability has been resolved:
ACPI: CPPC: Suppress UBSAN warning caused by field misuse
The definition of reg->accesswidth changes depending on the reg->spaceid type. Type ACPIADRSPACEPLATFORMCOMM 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/cppcacpi.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) ubsanepilogue+0x10/0x48 __ubsanhandleshiftoutofbounds+0xdc/0x1e0 cpcwrite+0x4d0/0x670 cppcsetperf+0x18c/0x490 cppccpufreqcpuinit+0x1c8/0x380 [cppccpufreq] ... (trimming)
Lets fix this by validating the region type, as well as whether accesswidth has a value. Then since we are returning bitwidth directly for ACPIADRSPACEPLATFORMCOMM, drop the code correcting the size.
{
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64512.json"
}