CVE-2025-40020: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-40020 is a vulnerability discovered in the Linux kernel's PEAK-USB CAN driver, specifically related to a shift-out-of-bounds issue. The vulnerability was disclosed on October 24, 2025, affecting various Linux kernel versions. The issue involves improper handling of bit shifting operations in the driver that supports PC CAN FD interfaces (NVD, Debian Tracker).

The vulnerability stems from a shift-out-of-bounds condition in the PEAK-USB CAN driver where a 32-bit shifting operation was performed without proper 64-bit constant usage. The issue has been assigned a CVSS v3.1 base score of 7.0 (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H), indicating high severity with local access requirements (Red Hat).

The vulnerability could potentially lead to memory corruption or system instability when exploited through the affected CAN FD interfaces. Multiple Linux distributions including Red Hat Enterprise Linux versions 7, 8, 9, and their real-time kernel variants are affected by this vulnerability (Red Hat).

The issue has been fixed in Linux kernel version 6.16.12-2 and later versions. Various Linux distributions have released or are in the process of releasing security updates to address this vulnerability. Debian has marked this as fixed in their 'forky' and 'sid' distributions (Debian Tracker).