Serv-U FTP server 3.0, 3.1 and 4.0.0.4 does not accept new connections while validating user folder access rights, which allows remote attackers to cause a denial of service (no new connections) via a series of MKD commands.
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.