CVE-2021-47386: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47386 affects the Linux kernel's hardware monitoring (hwmon) subsystem, specifically the w83791d driver. The vulnerability was discovered by the Linux Driver Verification project and involves a NULL pointer dereference issue in the driver's subclients detection functionality (Kernel Git).

The vulnerability occurs when the driver reads a specific value pattern where (val & 0x08) && (!(val & 0x80)) && ((val & 0x7) == ((val >> 4) & 0x7)) from the device, leading to a NULL pointer dereference. This can happen when tmp = 0b0xyz1xyz, where the same literals represent the same numbers. The issue is related to the unnecessary lm75[] structure field after switching to devm_i2c_new_dummy_device() in w83791d_detect_subclients() (Red Hat).

The vulnerability is rated as moderate severity as it can lead to system crashes or unexpected behavior, which can disrupt normal operations but does not directly compromise sensitive data or allow unauthorized access (Red Hat).

The vulnerability requires local access to the system and can be triggered through specific hardware monitoring operations. The CVSS v3.1 base score is 7.8 (High) with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

The issue has been fixed by removing the unnecessary lm75[] structure field and implementing proper error handling in the w83791d driver. Users are advised to update their systems with the patched kernel version (Kernel Git).