CVE-2025-37993 is a vulnerability identified in the Linux kernel's CAN (Controller Area Network) subsystem, specifically within the m_can driver. The issue arises because the spin lock named tx_handling_spinlock, which is part of the m_can_classdev structure, is not properly initialized during the device probe phase in the function m_can_class_allocate_dev(). This lack of initialization leads to a 'spinlock bad magic' error when the kernel attempts to send CAN frames, for example, using the cansend utility from can-utils. The error manifests as a kernel bug report indicating corrupted or uninitialized spinlock state, which can cause kernel instability or crashes. The root cause is that the spinlock's magic number, owner, and owner_cpu fields remain unset, triggering kernel warnings and potential deadlocks or race conditions during CAN frame transmission. The vulnerability was resolved by ensuring that the spinlock is properly initialized during device allocation, preventing the kernel from encountering invalid spinlock states. This vulnerability affects Linux kernel versions prior to the patch and is relevant to systems using the m_can CAN controller driver, which is common in embedded and automotive Linux environments.

For European organizations, the impact of CVE-2025-37993 depends largely on their use of Linux-based systems that incorporate the m_can CAN driver, typically found in embedded systems, automotive control units, industrial automation, and IoT devices. If exploited, this vulnerability could lead to kernel crashes or denial of service (DoS) conditions on affected devices, disrupting critical operations. In sectors such as automotive manufacturing, transportation, and industrial control systems prevalent in Europe, this could result in operational downtime, safety risks, and potential financial losses. While no known exploits are currently reported in the wild, the vulnerability's presence in the kernel could be leveraged by attackers with local access or through compromised software to destabilize systems. Confidentiality and integrity impacts are limited since the vulnerability primarily causes availability issues through kernel instability. However, in safety-critical environments, availability disruptions can have severe consequences. European organizations relying on embedded Linux devices with CAN bus communication should be particularly vigilant, as these devices are integral to vehicle networks and industrial machinery.

To mitigate CVE-2025-37993, organizations should: 1) Apply the official Linux kernel patches that initialize the tx_handling_spinlock in the m_can_class_allocate_dev() function as soon as they become available. 2) For embedded or automotive Linux systems, coordinate with hardware and software vendors to ensure updated kernel versions are deployed in devices using the m_can driver. 3) Conduct thorough testing of CAN-related functionality after patching to confirm stability and absence of spinlock errors. 4) Implement monitoring for kernel logs on CAN-enabled devices to detect any spinlock-related warnings or crashes indicative of unpatched systems. 5) Restrict local access to systems running vulnerable kernels to trusted personnel only, as exploitation requires local code execution or interaction with CAN utilities. 6) For critical infrastructure, consider network segmentation and strict access controls around embedded Linux devices to limit attack surface. 7) Maintain an inventory of devices using the m_can driver to prioritize patching and risk assessment.