CVE-2026-13478 Out-of-bounds read in Zephyr ext2 block-bitmap validation from a crafted s_blocks_count

The Zephyr ext2 filesystem driver validates the on-disk block bitmap in ext2initfs subsys/fs/ext2/ext2impl.c by passing fsblocks = sblockscount - sfirstdatablock to ext2bitmapcountset. That helper subsys/fs/ext2/ext2bitmap.c treats its argument as a number of bits and reads one bitmap byte per...