Server-Side Request Forgery (SSRF)
ftp-srv before 2.19.6, 3.x before 3.1.2, and 4.x before 4.3.4 are vulnerable to Server-Side Request Forgery. The PORT command allows arbitrary IPs which can be used to cause the server to make a connection elsewhere. A possible workaround is blocking the PORT through the configuration. This issue is fixed in version 4.3.4. More information can be found on the linked advisory.
CWE-918 - Server-Side Request Forgery (SSRF)
Server-side request forgery (SSRF) is a weakness that allows an attacker to send an arbitrary request, making it appear that the request was sent by the server. This request may bypass a firewall that would normally prevent direct access to the URL. The impact of this vulnerability can vary from unauthorized access to files and sensitive information to remote code execution.