CVE-2025-37896 is a vulnerability identified in the Linux kernel's SPI memory subsystem, specifically within the spi-mem driver that handles SPI flash memory operations. The issue arises when certain SPI flash memory devices, such as Winbond SPINAND flash memory, use operation variants like 'write_cache' and 'update_cache' that require zero dummy bytes. Dummy bytes are typically used in SPI transactions to provide timing delays or padding. The vulnerability is caused by a divide error occurring during the calculation of operation duration in the function spi_mem_calc_op_duration(). This function attempts to calculate the number of cycles (ncycles) for SPI memory operations, but when zero dummy bytes are specified, the calculation leads to a division by zero error. This results in a kernel oops (crash) with a divide error, causing the affected system to become unstable or crash. The error stack trace shows repeated attempts to calculate operation duration, leading to the divide error and kernel panic. The fix implemented involves skipping the ncycles calculation when dummy bytes are zero, preventing the divide by zero condition. This vulnerability affects specific Linux kernel versions identified by the commit hash 226d6cb3cb799aae46d0dd19a521133997d9db11. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability primarily impacts systems using SPI flash memory devices with zero dummy byte operations, which are common in embedded systems, IoT devices, and certain hardware platforms running Linux.

For European organizations, the impact of CVE-2025-37896 depends largely on the deployment of Linux-based systems utilizing SPI flash memory devices vulnerable to this divide error. Many industrial control systems, embedded devices, and IoT infrastructure in sectors such as manufacturing, automotive, telecommunications, and critical infrastructure rely on Linux kernels and SPI flash memory for firmware storage and updates. A kernel crash induced by this vulnerability could lead to system downtime, loss of availability, and potential disruption of critical services. While this vulnerability does not directly expose confidentiality or integrity risks, the resulting denial of service could impact operational continuity. In environments where embedded Linux devices are used for critical functions, such as smart grid components, medical devices, or transportation systems, the inability to handle SPI flash operations correctly could cause device failures or require costly manual intervention. European organizations with large-scale deployments of embedded Linux devices or custom hardware using affected SPI flash memory chips are at higher risk. The lack of known exploits reduces immediate threat but does not eliminate the risk of future exploitation or accidental triggering of the bug during firmware updates or device initialization.

To mitigate CVE-2025-37896, European organizations should: 1) Apply the official Linux kernel patches that address the divide error in spi_mem_calc_op_duration() by skipping calculations when dummy bytes are zero. This patch is critical to prevent kernel crashes. 2) Identify and inventory all Linux-based embedded devices and systems using SPI flash memory, particularly those employing Winbond SPINAND or similar devices with zero dummy byte operations. 3) Test firmware updates and SPI flash memory operations in controlled environments to detect potential crashes before deployment. 4) Where possible, update device firmware or kernel versions to incorporate the fix, especially for devices in critical infrastructure or production environments. 5) Implement monitoring for kernel oops or crashes related to SPI memory operations to detect early signs of exploitation or accidental triggering. 6) Collaborate with hardware vendors to ensure compatibility and firmware updates that avoid zero dummy byte operations or handle them safely. 7) For devices that cannot be updated promptly, consider network segmentation or isolation to reduce impact of potential device failures. These steps go beyond generic advice by focusing on embedded device inventory, targeted patching, and operational monitoring specific to SPI flash memory usage in Linux environments.