In the Linux kernel ACPI CPPC subsystem, the field reg->access_width is misinterpreted when the space_id is ACPI_ADR_SPACE_PLATFORM_COMM. This misuse can cause a UBSAN shift‑out‑of‑bounds violation, exposing the kernel to undefined behavior that may lead to instability or failure. The vulnerability is a classic example of undefined behavior (CWE‑1335). While the description does not explicitly state a crash, the UBSAN error indicates that kernel code is operating beyond defined bounds.

All Linux kernel builds that include the ACPI CPPC feature and have not incorporated the security fix. The vulnerability applies to any such kernel regardless of version until the patch is applied.

The CVSS score of 5.5 suggests a moderate severity. An EPSS score of less than 1% indicates a very low probability of real‑world exploitation, and the vulnerability is not listed in the CISA KEV catalog. The attack vector is not explicitly defined in the CVE description; it is inferred that an attacker would need to supply a malformed ACPI region definition, potentially via firmware or a privileged process, to trigger the UBSAN error. Therefore, the risk is moderate but unlikely under typical operational conditions.