The set_fat function in fat.c in dosfstools before 4.0 might allow attackers to corrupt a FAT12 filesystem or cause a denial of service (invalid memory read and crash) by writing an odd number of clusters to the third to last entry on a FAT12 filesystem, which triggers an "off-by-two error."

The read_boot function in boot.c in dosfstools before 4.0 allows attackers to cause a denial of service (crash) via a crafted filesystem, which triggers a heap-based buffer overflow in the (1) read_fat function or an out-of-bounds heap read in (2) get_fat function.