CVE-2025-39681: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-39681 is a vulnerability discovered in the Linux kernel affecting the x86/cpu/hygon component, specifically related to a missing resctrlcpudetect() call in the bspinit helper. The issue was disclosed on September 5, 2025, and affects systems with X86FEATURE_CQM* support (NVD).

The vulnerability stems from a code change introduced by commit 923f3a2b48bd which moved resctrlcpudetect() from common CPU initialization code to vendor-specific BSP init helper. However, Hygon's implementation failed to include this call in their code. This oversight results in a division by zero fault during early booting stage on machines with X86FEATURECQM* support, where getrdtmonresources() attempts to calculate monl3config with uninitialized bootcpudata.x86cacheoccscale (NVD).

The vulnerability can trigger a division by zero fault during the early booting stage on machines with X86FEATURECQM* support, potentially affecting system stability and boot processes (NVD).

The vulnerability has been resolved by adding the missing resctrlcpudetect() call in the Hygon BSP init helper (NVD).