CVE-2025-39818: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-39818 is a vulnerability discovered in the Linux kernel, specifically affecting the Intel THC HID driver component. The vulnerability was disclosed on September 16, 2025, and involves incorrect pointer arithmetic in I2C registers save functionality. The issue affects Red Hat Enterprise Linux 9 and 10, while earlier versions are not impacted (RedHat, NVD).

The vulnerability stems from improper use of a secondary pointer (&dev->i2csubipregs) which leads to a kernel crash and out-of-bounds error. The issue manifests as a KASAN slab-out-of-bounds error in the regmapbulk_read function, specifically writing 4 bytes at an invalid address. The CVSS 3.1 score is 7.0 with vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H (RedHat).

The vulnerability can cause kernel crashes and potential memory corruption through out-of-bounds write operations. The buggy address belongs to a kmalloc-rnd-12-192 cache object of size 192 bytes, with the out-of-bounds write occurring 0 bytes beyond the allocated region (NVD).

The vulnerability has been resolved by replacing the problematic pointer arithmetic with direct array indexing (&dev->i2csubipregs[i]) to ensure safe memory access. Users should update to the patched versions of affected Red Hat Enterprise Linux distributions (NVD).