CVE-2025-37751 is a vulnerability identified in the Linux kernel specifically related to the x86 CPU microcode handling for AMD processors. The issue arises from a programming error where the NULL array terminator at the end of the erratum_1386_microcode array was removed during a code refactor from x86_cpu_desc to x86_cpu_id. This removal causes code that reads this array to run off the end, potentially leading to undefined behavior such as memory corruption or crashes. The erratum table is used to apply microcode workarounds for known CPU bugs, and improper handling of this table can cause the kernel to misinterpret or mishandle CPU errata. Although no known exploits are currently reported in the wild, the vulnerability could be triggered by the kernel itself during CPU initialization or microcode update processes, potentially leading to system instability or denial of service. The vulnerability does not require user interaction or authentication to be triggered, as it is internal to kernel operations. The Linux kernel is widely used across many distributions and environments, including servers, desktops, and embedded systems, making this a broadly relevant issue. The patch involves restoring the NULL terminator to the erratum_1386_microcode array to prevent out-of-bounds reads and ensure safe iteration over the erratum entries.

For European organizations, the impact of CVE-2025-37751 could be significant, especially for those relying heavily on Linux-based infrastructure, including cloud service providers, data centers, and critical infrastructure operators. The vulnerability could lead to kernel crashes or unpredictable behavior during CPU microcode updates, potentially causing system downtime or degraded performance. This is particularly critical for environments requiring high availability and stability, such as financial institutions, healthcare providers, and government agencies. While no direct exploitation has been observed, the risk of denial of service or system instability could disrupt business operations and service delivery. Additionally, if attackers find a way to leverage this vulnerability in combination with other exploits, it could lead to more severe consequences. Given the widespread use of AMD processors in servers and workstations, the vulnerability's impact is non-trivial. Organizations with stringent uptime requirements and those operating in regulated sectors must prioritize addressing this issue to maintain operational integrity.

Organizations should promptly apply the official Linux kernel patches that restore the NULL terminator in the erratum_1386_microcode array. Since this is a kernel-level vulnerability, updating to the latest stable kernel version provided by their Linux distribution vendors is the most effective mitigation. For environments where immediate patching is challenging, organizations should monitor kernel logs for anomalies related to CPU microcode updates and consider temporarily limiting kernel updates or microcode refreshes until patched. Additionally, thorough testing of kernel updates in staging environments is recommended to prevent unexpected downtime. System administrators should also ensure that firmware and microcode updates from AMD are current and compatible with the patched kernel. Employing kernel hardening techniques and monitoring tools to detect unusual kernel behavior can provide additional layers of defense. Finally, organizations should maintain an inventory of systems running affected Linux kernel versions and prioritize patch deployment based on criticality and exposure.