A malicious server can use the FTP PASV response to trick curl 7.73.0 and earlier into connecting back to a given IP address and port, and this way potentially make curl extract information about services that are otherwise private and not disclosed, for example doing port scanning and service banner extractions.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:LI:NA:N3.7/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:NInformation Disclosure