The pr_data_xfer function in ProFTPD before 1.3.2rc3 allows remote authenticated users to cause a denial of service (CPU consumption) via an ABOR command during a data transfer.
ProFTPD 1.2.x, including 1.2.8 and 1.2.10, responds in a different amount of time when a given username exists, which allows remote attackers to identify valid usernames by timing the server response.