CVE-2024-56651 is a high-severity vulnerability identified in the Linux kernel's CAN (Controller Area Network) driver, specifically within the hi311x CAN controller interface. The issue arises from a use-after-free condition in the hi3110_can_ist() function. The root cause is linked to a prior commit (a22bd630cfff) that altered the behavior of error reporting for CAN frames by suppressing the reporting of transmit (txerr) and receive (rxerr) errors even when the bus was operating correctly (i.e., not in a bus-off state). This change introduced a flaw where error count information was appended to CAN frames after the netif_rx() function call. Since netif_rx() schedules the packet (skb) for reception and potentially frees or reuses it asynchronously, accessing or modifying the skb after this call can lead to a use-after-free condition. This vulnerability is categorized under CWE-416 (Use After Free), which can lead to memory corruption, system crashes, or arbitrary code execution depending on the exploitation context. The fix involves deferring the netif_rx() call when txerr and rxerr reporting is needed, ensuring that the skb is not accessed after it may have been freed. The vulnerability affects multiple Linux kernel versions identified by specific commit hashes, indicating a range of affected kernel builds. The CVSS v3.1 base score is 7.8, reflecting high severity due to its impact on confidentiality, integrity, and availability, with low attack complexity, requiring low privileges and no user interaction. No known exploits are currently reported in the wild, but the nature of the vulnerability warrants prompt attention and patching.

For European organizations, this vulnerability poses significant risks, especially those relying on Linux-based systems for critical infrastructure, industrial control systems, automotive applications, or embedded devices that utilize CAN bus communication. Exploitation could allow attackers with local access or limited privileges to execute arbitrary code, cause denial of service through kernel crashes, or escalate privileges, compromising system confidentiality, integrity, and availability. Given the widespread use of Linux in servers, IoT devices, and embedded systems across Europe, unpatched systems could be targeted in sectors such as manufacturing, automotive, energy, and telecommunications. The potential for disruption in industrial environments is particularly concerning, as CAN bus is commonly used in automotive and industrial automation. The vulnerability could also impact cloud service providers and enterprises running Linux kernels with affected versions, leading to broader service interruptions or data breaches.

European organizations should prioritize applying the official Linux kernel patches that address CVE-2024-56651 as soon as they become available. In environments where immediate patching is not feasible, organizations should: 1) Restrict local access to systems running vulnerable kernel versions to trusted personnel only, minimizing the risk of exploitation. 2) Monitor kernel logs and CAN interface activity for unusual error reporting or anomalies that could indicate exploitation attempts. 3) Employ kernel hardening techniques such as enabling Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce exploitation success. 4) For embedded and automotive systems, coordinate with device vendors to ensure firmware updates incorporate the fix. 5) Implement network segmentation to isolate CAN bus devices from general IT networks, limiting attack surface. 6) Conduct thorough inventory and vulnerability scanning to identify all affected Linux kernel versions in use. 7) Develop incident response plans specifically addressing kernel-level compromises and use-after-free exploitation scenarios.