Linux Kernel CVE-2026-53015

EROFS (Enhanced Read-Only File System) is a compressed, space-efficient read-only filesystem introduced in Linux 5.3, commonly used in Android and embedded systems. The root cause is an integer width mismatch: the lcn (logical cluster number) variable was declared as unsigned long or unsigned int, which is only 32 bits wide on 32-bit architectures (CPE: cpe:2.3:a:linux:linux). When the kernel computes lcn << lclusterbits to derive a byte offset, the result silently wraps at 4 GiB (2^32), producing a corrupted address for any cluster residing beyond that boundary. The fix unifies lcn as the explicit u64 type throughout the EROFS codebase to guarantee 64-bit arithmetic regardless of the host architecture. While no CWE is formally assigned, the root cause class is an implicit type narrowing / integer truncation error analogous to CWE-190 (Integer Overflow) or CWE-681 (Incorrect Conversion Between Numeric Types).