CVE-2026-68478

In the Linux kernel, the following vulnerability has been resolved:

memstick: ms_block: reject a card that reports too many blocks

msb_ftl_initialize() computes the zone count from the card block count

with no bound:

msb->zone_count = msb->block_count / MS_BLOCKS_IN_ZONE;

...

for (i = 0; i < msb->zone_count; i++)

msb->free_block_count[i] = MS_BLOCKS_IN_ZONE;

msb->block_count is a card value. msb_read_boot_blocks() reads

number_of_blocks from the card boot page and byte swaps it.

free_block_count is a fixed int[MS_MAX_ZONES]. MS_MAX_ZONES is 16, so the

valid indices are 0 to 15. The init loop above indexes it by zone_count.

msb_mark_block_used() and msb_mark_block_unused() index it by

pba / MS_BLOCKS_IN_ZONE, for pba up to block_count - 1. A card may report

up to 65535 blocks. A block_count above 8192 (MS_MAX_ZONES *

MS_BLOCKS_IN_ZONE) lets the pba index reach 16. That writes past

free_block_count[] and corrupts struct msb_data. A larger count runs the

init loop past the end too.

A real Memory Stick has at most 16 zones. So it has at most 8192 blocks.

msb_ftl_initialize() now rejects a card that reports more than

MS_MAX_ZONES * MS_BLOCKS_IN_ZONE blocks.