The glob functionality in ProFTPD 1.2.1, and possibly other versions allows remote attackers to cause a denial of service (CPU and memory consumption) via commands with large numbers of wildcard and other special characters, as demonstrated using an ls command with multiple (1) "*/..", (2) "*/.*", or (3) ".*./*?/" sequences in the argument.
http://www.mandriva.com/security/advisories?name=MDKSA-2002:005
http://online.securityfocus.com/archive/1/169395
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000450