CVE-2023-52635 is a vulnerability identified in the Linux kernel's devfreq subsystem, specifically related to the synchronization of devfreq_monitor_start and devfreq_monitor_stop functions. The devfreq driver manages dynamic frequency scaling for devices to optimize power consumption and performance. The vulnerability arises when there is a rapid, repeated switching of the frequency governor in a loop, which can lead to corruption of the timer list. This occurs because timer cancellation is invoked concurrently from two different contexts: cancel_delayed_work_sync() and expire_timers(). The lack of proper synchronization allows delayed work structures to become corrupted while they are being queued, running, or cancelled. This can cause kernel timer corruption and ultimately lead to kernel crashes or system instability, as evidenced by kernel oops and memory abort errors in the provided traces. The root cause is a race condition in the devfreq driver where the start and stop operations are not adequately synchronized, allowing multiple timer instances to be queued or cancelled simultaneously, leading to use-after-free or invalid memory access. The fix involves introducing a polling flag and a devfreq lock to ensure proper synchronization of timer queueing and cancellation, preventing corruption of the delayed work data structures. This vulnerability affects Linux kernel versions prior to the patch and is particularly relevant for systems using the devfreq driver, such as embedded devices and mobile platforms running Linux kernels with Qualcomm hardware. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2023-52635 depends largely on their use of Linux-based systems that utilize the devfreq driver, especially those running on Qualcomm hardware or similar embedded platforms. The vulnerability can cause kernel crashes and system instability, potentially leading to denial of service (DoS) conditions. This can disrupt critical services, particularly in sectors relying on embedded Linux devices such as telecommunications infrastructure, industrial control systems, automotive systems, and IoT deployments. In environments where uptime and reliability are critical, such as healthcare, manufacturing, and financial services, this vulnerability could lead to operational disruptions. Although there is no evidence of privilege escalation or remote code execution, the kernel panic and memory corruption could be leveraged by attackers with local access to cause service outages or to facilitate further attacks by destabilizing the system. The lack of requirement for user interaction suggests that automated or scripted attacks could trigger the vulnerability if local access is obtained. Given the widespread use of Linux in European IT infrastructure and embedded systems, the vulnerability poses a moderate risk, especially for organizations with embedded Linux devices or custom Linux kernels that have not yet applied the patch.

European organizations should prioritize the following mitigation steps: 1) Identify and inventory all Linux systems, particularly embedded devices and servers running kernels with devfreq support, especially those on Qualcomm or similar hardware platforms. 2) Apply the official Linux kernel patches that address CVE-2023-52635 as soon as they become available from trusted sources or Linux distribution vendors. 3) For devices where kernel patching is not immediately feasible, implement operational controls to limit rapid governor switching or disable devfreq governor switching loops in software configurations to reduce the risk of triggering the vulnerability. 4) Monitor system logs and kernel traces for signs of timer corruption or kernel oops related to devfreq operations to detect potential exploitation attempts or instability. 5) Restrict local access to trusted users and enforce strict access controls to prevent unauthorized users from triggering the vulnerability. 6) Engage with hardware and software vendors to ensure timely updates and support for affected embedded devices. 7) Incorporate this vulnerability into vulnerability management and patching cycles, ensuring embedded and IoT devices are not overlooked. These steps go beyond generic advice by focusing on embedded device management, kernel patching, and operational controls specific to the devfreq subsystem.