Serv-U FTP server 4.x and 5.x allows remote attackers to cause a denial of service (application crash) via a STORE UNIQUE (STOU) command with an MS-DOS device name argument such as (1) COM1, (2) LPT1, (3) PRN, or (4) AUX.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17329