source: https://www.securityfocus.com/bid/1387/info
  
Washington University ftp daemon (wu-ftpd) is a very popular unix ftp server shipped with many distributions of Linux and other UNIX operating systems. Wu-ftpd is vulnerable to a very serious remote attack in the SITE EXEC implementation. Because of user input going directly into a format string for a *printf function, it is possible to overwrite important data, such as a return address, on the stack. When this is accomplished, the function can jump into shellcode pointed to by the overwritten eip and execute arbitrary commands as root. While exploited in a manner similar to a buffer overflow, it is actually an input validation problem. Anonymous ftp is exploitable making it even more serious as attacks can come anonymously from anywhere on the internet.
  
It should be noted that the SITE INDEX command is affected as well. 

https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/20032.tar.gz