The passthrough FTP feature on Cisco Web Security Appliance (WSA) devices with software 8.0.7-142 and 8.5.1-021 allows remote attackers to cause a denial of service (CPU consumption) via FTP sessions in which the control connection is ended after data transfer, aka Bug ID CSCut94150.
The proxy process on Cisco Web Security Appliance (WSA) devices through 9.1.0-070 allows remote attackers to cause a denial of service (CPU consumption) by establishing an FTP session and then improperly terminating the control connection after a file transfer, aka Bug ID CSCuy43468.