CVE-2021-46995 is a vulnerability identified in the Linux kernel specifically within the CAN (Controller Area Network) subsystem driver for the MCP251xfd device, which is a CAN FD (Flexible Data-rate) controller. The issue arises in the function mcp251xfd_probe(), which is responsible for initializing the device when the driver is loaded. During a code refactor to use dev_err_probe(), a return statement was inadvertently removed. This omission causes the function to continue execution even when devm_clk_get() fails to acquire a clock resource. As a result, the subsequent call to clk_get_rate() operates on a NULL or invalid pointer, leading to a kernel oops, which is a form of kernel panic or crash. This error pointer dereference can cause a denial of service (DoS) by crashing the kernel and potentially destabilizing the affected system. The vulnerability does not appear to have known exploits in the wild as of the publication date, and no CVSS score has been assigned yet. The affected versions are specific commits identified by their hashes, indicating that this is a recent and targeted fix in the Linux kernel source. The vulnerability is rooted in improper error handling and pointer dereferencing in kernel space, which is critical because kernel crashes affect system availability and stability. Since this is a kernel-level issue, exploitation requires the vulnerable driver to be present and loaded, and the system to be running the affected kernel version. User interaction is not necessarily required, but local access or conditions that trigger the driver probe may be needed. This vulnerability is primarily a stability and availability concern rather than a direct confidentiality or integrity compromise.

For European organizations, the impact of CVE-2021-46995 centers on system availability and operational continuity. Systems running Linux kernels with the vulnerable MCP251xfd CAN driver could experience unexpected kernel crashes, leading to service interruptions. This is particularly relevant for industries relying on embedded Linux systems or IoT devices that use CAN bus communications, such as automotive manufacturing, industrial automation, and transportation infrastructure. Disruptions in these environments could affect production lines, vehicle diagnostics, or critical control systems. While the vulnerability does not directly expose data or allow privilege escalation, the denial of service caused by kernel crashes can result in downtime, loss of productivity, and potential safety risks in critical systems. European organizations with Linux-based infrastructure should be aware of this vulnerability to prevent unexpected outages, especially in sectors where CAN bus devices are integral. The lack of known exploits reduces immediate risk, but the presence of the vulnerability in widely used Linux kernels means that timely patching is essential to maintain system reliability.

To mitigate CVE-2021-46995, organizations should: 1) Identify and inventory Linux systems running kernels that include the MCP251xfd CAN driver, especially those with the affected commit hashes or versions. 2) Apply the official Linux kernel patches that fix the missing return statement in mcp251xfd_probe(), ensuring that error handling correctly prevents dereferencing invalid pointers. 3) If immediate patching is not feasible, consider disabling the MCP251xfd driver or the CAN subsystem if it is not in use, to reduce exposure. 4) Monitor system logs for kernel oops or crashes related to the CAN subsystem to detect potential triggering of this vulnerability. 5) For embedded or IoT devices, coordinate with vendors to obtain updated firmware or kernel versions that incorporate the fix. 6) Implement robust system monitoring and automated reboot strategies to minimize downtime in case of unexpected kernel crashes. 7) Maintain strict access controls to limit local access to systems where exploitation could be triggered, as local conditions may be required to activate the vulnerability. These steps go beyond generic advice by focusing on driver-specific mitigation, inventory management, and operational monitoring tailored to the nature of this kernel vulnerability.