It indicates a possible exploit of a denial of service vulnerability in acFTP.
This flaw is due to an error when processing a malformed argument passed to the "REST" or "PBSZ" command, which could be exploited by attackers to crash a vulnerable application, creating a denial of service condition.
acFTP version 1.5 and prior.
Denial of service.
Currently we are not aware of any vendor-supplied patches for this issue.