CVE-2025-38004 is a vulnerability identified in the Linux kernel's CAN broadcast manager (CAN BCM) subsystem. The CAN BCM is responsible for managing sequences of CAN (Controller Area Network) frames, which are used extensively in automotive and industrial control systems for communication between microcontrollers and devices. The vulnerability arises from improper synchronization when updating runtime variables such as 'currframe' and 'count' within the bcm_can_tx() function. These variables track the current frame in the sequence and the count of frames to be sent, respectively. Both can be modified concurrently from user space and the high-resolution timer (hrtimer) context without adequate locking mechanisms. This race condition leads to a slab-out-of-bounds read detected by Kernel Address Sanitizer (KASAN), which indicates a potential for memory corruption. The root cause is the lack of a spin_lock_bh (bottom half spinlock) protecting these updates, allowing concurrent access and modification. The patch involves adding proper locking around these critical sections and moving the 'count' variable inside the protected region to prevent concurrent modification. Although no known exploits are currently in the wild, the vulnerability could be leveraged to cause kernel crashes or potentially escalate privileges by corrupting kernel memory. The affected versions are specific Linux kernel commits identified by their hashes, indicating this is a recent and targeted fix. Since the CAN BCM is primarily used in embedded and automotive Linux environments, the impact is more pronounced in systems relying on CAN bus communication.

For European organizations, especially those in automotive manufacturing, industrial automation, and embedded systems sectors, this vulnerability poses a significant risk. Many European countries have strong automotive industries (e.g., Germany, France, Italy) where Linux-based embedded systems with CAN bus interfaces are common. Exploitation could lead to denial of service through kernel crashes or, in worst cases, privilege escalation allowing attackers to gain control over critical systems. This could disrupt manufacturing lines, compromise vehicle safety systems, or affect industrial control systems, leading to operational downtime and safety hazards. Additionally, organizations involved in developing or deploying IoT devices with CAN interfaces could face increased risk. Given the increasing adoption of Linux in automotive ECUs and industrial controllers, the vulnerability could have broad implications for supply chain security and operational continuity in Europe.

Organizations should immediately apply the official Linux kernel patches that introduce spin_lock_bh protection in the bcm_can_tx() function and move the 'count' variable into the protected critical section. For embedded and automotive Linux systems, kernel updates should be tested and deployed promptly. Where immediate patching is not feasible, organizations should restrict unprivileged user access to CAN BCM interfaces to prevent exploitation from user space. Implementing strict access controls and monitoring for unusual CAN bus activity can help detect attempts to exploit this race condition. Additionally, enabling kernel hardening features such as KASAN in development environments can assist in early detection of memory corruption issues. Vendors and integrators should review their CAN BCM usage and consider additional synchronization mechanisms if custom modifications exist. Finally, continuous monitoring of Linux kernel advisories and rapid deployment of security updates is critical to mitigate emerging risks.