The makemask function in mountd.c in mountd in FreeBSD 7.4 through 8.2 does not properly handle a -network field specifying a CIDR block with a prefix length that is not an integer multiple of 8, which allows remote attackers to bypass intended access restrictions in opportunistic circumstances via an NFS mount request.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.