cve 2025 21991

CVE-2025-21991 is a Linux kernel vulnerability in the AMD microcode loader that affects systems with CPU-less NUMA nodes. The bug is an out-of-bounds access in the arch/x86 AMD microcode path, which can cause memory corruption and lead to system instability or denial-of-service during microcode updates. This issue is particularly relevant for administrators managing NUMA-based servers, as it may occur during maintenance windows. The fix addresses the bounds-checking flaw to prevent potential crashes. While the vulnerability is specific to Linux, it is of interest to WindowsForum.com readers who manage mixed-OS environments or virtualized systems where Linux guests run on AMD hardware.