OPIE off-by-one stack overflow nmap .nse script file.
You can download it from the following link: https://packetstormsecurity.com/files/download/90040/ftp-libopie.nse
Source: https://packetstormsecurity.com/files/90040/OPIE-Off-By-One-Stack-Overflow-Nmap-NSE-Script.html