CVE-2023-52637 is a use-after-free (UAF) vulnerability identified in the Linux kernel's Controller Area Network (CAN) subsystem, specifically within the J1939 protocol implementation. The vulnerability occurs in the function j1939_sk_match_filter during the handling of setsockopt calls with the SO_J1939_FILTER option. The root cause is a race condition where the socket's filter list (jsk->filters) is modified concurrently while packets are being received, leading to a use-after-free scenario. This is due to the lack of proper locking around the socket structure (jsk->sk) when modifying filters, allowing the kernel to access freed memory. The vulnerability was detected by Kernel Address Sanitizer (KASAN), which reported slab-use-after-free errors during packet reception. Exploitation of this flaw could lead to kernel memory corruption, potentially causing system crashes (denial of service) or enabling privilege escalation if an attacker can manipulate kernel memory. The vulnerability affects Linux kernel versions prior to the patch that introduced locking to prevent concurrent modification of filters. The affected versions are identified by specific git commit hashes, indicating this is a recent and targeted fix. No public exploits are known at this time, and the vulnerability was published on April 3, 2024. The vulnerability requires the ability to invoke setsockopt with SO_J1939_FILTER and to send/receive CAN J1939 packets, which typically requires local access or control over CAN network interfaces. The J1939 protocol is used primarily in automotive and industrial control systems for communication over CAN buses, which are common in embedded and specialized Linux deployments rather than general-purpose desktop or server environments.

For European organizations, the impact of CVE-2023-52637 depends largely on their use of Linux systems with CAN J1939 protocol support. Industries such as automotive manufacturing, transportation, heavy machinery, and industrial automation in Europe often deploy embedded Linux systems with CAN bus interfaces for vehicle and equipment control. Exploitation of this vulnerability could allow attackers with local access to cause kernel crashes, leading to denial of service in critical control systems. More severely, if exploited for privilege escalation, attackers could gain kernel-level control, compromising system integrity and potentially enabling further lateral movement or sabotage. Given the specialized nature of the J1939 protocol, typical IT infrastructure (e.g., web servers, office desktops) is unlikely to be affected. However, organizations involved in automotive supply chains, industrial control systems, or critical infrastructure that rely on embedded Linux with CAN support could face operational disruptions or safety risks. The lack of known exploits reduces immediate risk, but the vulnerability's presence in kernel code used in embedded devices means that patching and mitigation are critical to prevent future targeted attacks. Additionally, the vulnerability could be leveraged in supply chain attacks targeting embedded Linux devices manufactured or maintained in Europe.

1. Apply the official Linux kernel patches that introduce locking around jsk->sk to prevent concurrent modification of filters, as soon as they become available in your kernel distribution. 2. For embedded devices or systems using custom kernels, backport the fix from the upstream Linux kernel to ensure protection. 3. Restrict access to CAN network interfaces and limit the ability to invoke setsockopt with SO_J1939_FILTER to trusted users only, minimizing the attack surface. 4. Implement strict access controls and monitoring on systems with CAN J1939 support to detect anomalous setsockopt calls or unusual CAN traffic patterns. 5. Where possible, isolate embedded Linux devices with CAN interfaces from general IT networks to reduce risk of remote exploitation. 6. Conduct thorough testing of updated kernels in controlled environments before deployment to ensure stability and compatibility with CAN-dependent applications. 7. Maintain an inventory of devices using CAN J1939 protocol and ensure timely updates as part of patch management processes. 8. Engage with device vendors and suppliers to confirm that they have applied the fix in their Linux kernel versions and firmware releases.