CVE-2023-54285: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54285 is an integer overflow vulnerability in the Linux kernel's iomap_write_delalloc_scan function that can lead to an out-of-bounds memory write on 32-bit systems. The root cause is that folio_next_index() returns an unsigned long value which, when left-shifted by PAGE_SHIFT, can overflow on 32-bit architectures. Affected kernel versions include 6.1.92 through 6.1.161 and 6.2 through 6.5.4. The vulnerability was published on December 30, 2025, and carries a CVSS v3.1 base score of 7.8 (High) (Feedly, Debian LTS Announce).

The vulnerability is classified as CWE-787 (Out-of-bounds Write) and stems from improper arithmetic in the iomap_write_delalloc_scan function within the Linux kernel's iomap subsystem. On 32-bit systems, the expression folio_next_index() << PAGE_SHIFT can overflow because the result exceeds the 32-bit unsigned long range; the fix replaces this with folio_pos(folio) + folio_size(folio), which correctly computes the folio's end position without overflow. Exploitation requires local access with low privileges, and no special user interaction is needed. Patches are available in the Linux kernel stable tree (Kernel Patch 1, Kernel Patch 2).

A local attacker with low privileges on a 32-bit Linux system could trigger the overflow to write data out-of-bounds in kernel memory, potentially causing memory corruption. Depending on which memory regions are overwritten, this could result in data integrity violations, unauthorized disclosure of sensitive kernel or user data, or system crashes leading to denial of service. The scope is limited to the local system, but memory corruption primitives can sometimes be chained for privilege escalation (Feedly).

Upgrade the Linux kernel to version 6.1.162 or later for systems running the 6.1.x series, or to version 6.5.5 or later for systems running the 6.2–6.5 series. Debian has issued advisories (DSA-6127-1 and DLA-4476-1) covering this fix for affected distributions. Prioritize patching 32-bit systems, as 64-bit systems are not directly vulnerable to this overflow condition. Test kernel updates in a staging environment before deploying to production (Debian LTS Announce, Linux Security Debian).