CVE-2025-37846 is a vulnerability identified in the Linux kernel specifically affecting the ARM64 architecture's MOPS (Memory Operations) exception handling code. The issue arises from improper handling of the source register during a SET* operation within the kernel's exception processing routine do_el0_mops(). In this context, the source register (src reg) should not be dereferenced for SET* operations because it is architecturally unused and can be reported as register 31 (XZR), which is the zero register in ARM64. Dereferencing this register leads to an out-of-bounds array access error detected by the Undefined Behavior Sanitizer (UBSAN). Prior to the patch identified by commit 2de451a329cf662b, the code used pt_regs_read_reg(), which prevented this out-of-bounds access, but changes introduced a regression causing the vulnerability. Although this vulnerability does not appear to have known exploits in the wild and lacks a CVSS score, it represents a potential stability and security risk in ARM64 Linux kernel environments. The flaw could cause kernel crashes or undefined behavior when the MOPS exception is triggered with a SET* sequence involving the zero register, potentially leading to denial of service or other unpredictable kernel-level faults. This vulnerability is relevant for Linux kernel versions containing the specified commit and affects systems running ARM64 processors, which are increasingly common in servers, embedded devices, and cloud infrastructure. The vulnerability is subtle and requires specific conditions to trigger, but it highlights the importance of careful register handling in low-level kernel exception code.

For European organizations, the impact of CVE-2025-37846 primarily concerns systems running Linux on ARM64 architectures, including servers, cloud infrastructure, and embedded devices. While no active exploits are known, the vulnerability could lead to kernel crashes or instability, resulting in denial of service conditions. This can disrupt critical services, especially in sectors relying on ARM64-based Linux systems such as telecommunications, cloud providers, and IoT deployments. Confidentiality and integrity impacts appear limited as the vulnerability relates to out-of-bounds reads rather than direct memory corruption or privilege escalation. However, availability could be significantly affected if attackers or faulty software trigger the MOPS exception with the problematic SET* sequence, causing system crashes or reboots. European organizations using ARM64 Linux kernels in production environments should be aware of potential service disruptions and the need for timely patching. The vulnerability also underscores the importance of rigorous kernel testing and monitoring for unusual exception conditions that could indicate exploitation attempts or stability issues.

To mitigate CVE-2025-37846, European organizations should: 1) Identify all Linux systems running on ARM64 architectures, including servers, embedded devices, and cloud instances. 2) Track Linux kernel versions and apply the patch containing commit 2de451a329cf662b or later updates that address this vulnerability as soon as they become available. 3) Implement kernel-level monitoring to detect unusual MOPS exceptions or kernel faults that could indicate attempts to trigger this vulnerability. 4) For critical systems where immediate patching is not feasible, consider deploying kernel live patching solutions that can apply fixes without rebooting. 5) Engage with Linux distribution vendors and cloud providers to confirm patch availability and deployment timelines. 6) Conduct thorough regression testing after patch application to ensure system stability, given the subtle nature of the vulnerability. 7) Review and harden exception handling and kernel debugging configurations to facilitate rapid detection and response to related faults. These steps go beyond generic advice by focusing on ARM64-specific environments and emphasizing proactive monitoring and patch management tailored to kernel exception handling.