Format string vulnerability in wu-ftp 2.6.1 and earlier, when running with debug mode enabled, allows remote attackers to execute arbitrary commands via a malformed argument that is recorded in a PASV port assignment.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6020
http://www.debian.org/security/2001/dsa-016
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000443