CVE-2023-54295: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54295 is a shift-out-of-bounds vulnerability in the Linux kernel's MTD SPI-NOR subsystem, specifically in the spi_nor_set_erase_type() function within drivers/mtd/spi-nor/core.c. The flaw is triggered when the function is used to mask out an erase type, causing UBSAN to report a shift exponent of 4294967295 — far too large for a 32-bit integer. It affects Linux kernel versions from 4.20 up to the patched stable releases (5.10.173, 5.15.99, 6.1.16, 6.2.3, and 6.3). The vulnerability was published on December 30, 2025, with an EPSS score of approximately 0.018% (Feedly).

The root cause is an improper shift operation (CWE-125/CWE-190 class — undefined behavior via out-of-bounds shift) in spi_nor_set_erase_type() in drivers/mtd/spi-nor/core.c at line 2237. When the function is called to mask out (disable) an erase type by setting its size to zero, it still attempts to compute size_shift and size_mask using the zero size value, resulting in a shift exponent of 4294967295 (i.e., (uint32_t)-1) which is undefined behavior for a 32-bit integer type. The fix simplifies the masking path to only set the erase size to zero, since the rest of the codebase uses only the erase size to determine whether an erase type is supported — eliminating the unnecessary and erroneous shift operations (Feedly).

The vulnerability causes undefined behavior (UBSAN-detected shift-out-of-bounds) in the Linux kernel's SPI-NOR flash driver, which could lead to kernel instability or crashes on systems using SPI-NOR flash memory. The primary availability impact is a potential kernel panic or system crash on affected embedded or server hardware with SPI-NOR storage. Confidentiality and integrity impacts are considered low, as this is a local kernel driver bug rather than a remotely exploitable code execution flaw (Feedly).

The Linux kernel stable tree has released fixes across multiple stable branches. Patched versions include Linux 5.10.173, 5.15.99, 6.1.16, 6.2.3, and 6.3. The fix commits are available at the kernel stable repository for each affected branch. Users should update to the patched kernel version corresponding to their distribution's stable branch. No configuration-based workaround is available; upgrading the kernel is the recommended remediation (Feedly).