CVE-2021-47231 is a medium-severity vulnerability affecting the Linux kernel, specifically within the SocketCAN driver for the Microchip CAN BUS Analyzer Tool (mcba_usb). The issue is a memory leak caused by the improper handling of usb_coherent buffers allocated in the mcba_usb_start() function. In this function, 20 coherent buffers are allocated but are not properly freed when the device disconnects or when the USB Request Blocks (URBs) are killed. The disconnect function kills URBs without setting the URB_FREE_BUFFER flag, which cannot be used with coherent buffers, leading to persistent memory leaks. This flaw was identified by Syzbot, a kernel fuzzing tool, which reported multiple suspected memory leaks in the kernel memory leak detector (kmemleak). The vulnerability does not impact confidentiality or integrity but affects availability by causing resource exhaustion due to unreleased memory buffers. The same pattern of allocation and freeing coherent buffers is also present in the kvaser_usb_core.c driver, suggesting potential similar issues there. The vulnerability requires local access with low privileges (PR:L) and no user interaction (UI:N) but has limited attack surface since it is tied to the CAN BUS USB driver. The CVSS score is 5.5, reflecting a medium severity primarily due to its impact on availability and the need for local privileges. No known exploits are reported in the wild as of the publication date. The fix involves explicitly freeing the allocated usb_coherent buffers using usb_free_coherent() to prevent memory leaks and ensure proper resource management.

For European organizations, the primary impact of CVE-2021-47231 lies in potential denial-of-service conditions on Linux systems utilizing the affected SocketCAN drivers for Microchip CAN BUS Analyzer Tools. Organizations relying on embedded Linux systems or industrial control systems (ICS) that use CAN BUS interfaces for vehicle diagnostics, manufacturing automation, or IoT devices could experience degraded system stability or crashes due to memory exhaustion. This could disrupt critical operations, especially in automotive, manufacturing, and transportation sectors prevalent in Europe. Since the vulnerability requires local access, the risk is higher in environments where untrusted users or processes have access to the affected systems. Although the vulnerability does not allow data leakage or privilege escalation, the availability impact could lead to operational downtime and increased maintenance costs. The absence of known exploits reduces immediate risk, but unpatched systems remain vulnerable to potential future exploitation or accidental system failures. European organizations with Linux-based CAN BUS tools should prioritize patching to maintain system reliability and avoid disruptions in safety-critical environments.

1. Apply the latest Linux kernel patches that address CVE-2021-47231 as soon as they become available from trusted Linux distributions or kernel maintainers. 2. Audit systems using SocketCAN drivers, specifically those employing Microchip CAN BUS Analyzer Tools, to identify affected kernel versions and drivers. 3. Restrict local access to systems running these drivers to trusted administrators and processes only, minimizing the risk of exploitation by unprivileged users. 4. Implement monitoring of kernel memory usage and enable kmemleak or similar kernel memory leak detection tools to identify abnormal memory consumption patterns indicative of this vulnerability. 5. For embedded or industrial systems where patching may be delayed, consider isolating affected devices from untrusted networks and users to reduce attack surface. 6. Review and update device driver code if custom or legacy drivers are in use, ensuring proper usb_free_coherent() calls are implemented to prevent similar leaks. 7. Maintain an inventory of Linux kernel versions and CAN BUS hardware in use to streamline vulnerability management and patch deployment.