In uftpd before 2.11, there is a buffer overflow vulnerability in handle_PORT in ftpcmd.c that is caused by a buffer that is 16 bytes large being filled via sprintf() with user input based on the format specifier string %d.%d.%d.%d. The 16 byte size is correct for valid IPv4 addresses (len(&#39;255.255.255.255&#39;) == 16), but the format specifier %d allows more than 3 digits. This has been fixed in version 2.11