Guild FTPd allows remote attackers to determine the existence of files outside the FTP root via a .. (dot dot) attack, which provides different error messages depending on whether the file exists or not.
https://exchange.xforce.ibmcloud.com/vulnerabilities/4922
https://euvd.enisa.europa.eu/vulnerability/EUVD-2000-0636
http://www.securityfocus.com/bid/1452
http://archives.neohapsis.com/archives/bugtraq/2000-07/0114.html