CVE-2025-39788: 
Linux Debian vulnerability analysis and mitigation

In the Linux kernel, a vulnerability (CVE-2025-39788) was identified in the SCSI UFS Exynos driver. The issue involves incorrect programming of HCIUTRLNEXUS_TYPE on Google gs101 devices, where the number of UTP transfer request slots (nutrs) is 32. The vulnerability stems from a type casting issue where shifting operations result in undefined behavior (Debian Security).

The vulnerability occurs when the left-hand side of the shift operation is 1, which is of type int (31 bits wide). Shifting by more than the width results in undefined behavior. This leads to incorrect value being written to UTRLNEXUSTYPE (0xffffffff on gs101). The issue also triggers a UBSAN shift-out-of-bounds warning in drivers/ufs/host/ufs-exynos.c:1113:21, where the shift exponent 32 is too large for 32-bit type 'int' (Debian Security).

The vulnerability affects multiple Linux kernel versions in Debian distributions, including bullseye (5.10.223-1 and 5.10.237-1), bookworm (6.1.148-1 and 6.1.147-1), trixie (6.12.43-1 and 6.12.41-1), and forky (6.16.3-1). The issue has been fixed in sid version 6.16.6-1 (Debian Security).

The vulnerability has been fixed in the Linux kernel version 6.16.5-1 in the unstable (sid) distribution. The fix involves switching to the BIT() macro, which applies correct type casting as required. This ensures the correct value is written to UTRLNEXUSTYPE and fixes the UBSAN shift warning (Debian Security).