The ufs_lookup function in the Mac OS X 10.4.8 and FreeBSD 6.1 kernels allows local users to cause a denial of service (kernel panic) and possibly corrupt other filesystems by mounting a crafted UNIX File System (UFS) DMG image that contains a corrupted directory entry (struct direct), related to the ufs_dirbad function.  NOTE: a third party states that the FreeBSD issue does not cross privilege boundaries.