The remote host is vulnerable to a flaw that allows for the bypassing of authentication.
The remote host is using ProFTPD, a free FTP server for Unix and Linux. According to its banner, the version of ProFTPD installed on the remote host suffers from a flaw where a user can bypass access controls. An attacker exploiting this flaw would need the ability to authenticate to the server. Successful exploitation would result in the attacker elevating privileges or accessing confidential data.
Upgrade to version 1.3.0rc4 or higher.