Improper Input Validation
The dataconn function in ftpd.c in netkit ftpd (netkit-ftpd) 0.17, when certain modifications to support SSL have been introduced, calls fclose on an uninitialized file stream, which allows remote attackers to cause a denial of service (daemon crash) and possibly have unspecified other impact via some types of FTP over SSL protocol behavior, as demonstrated by breaking a passive FTP DATA connection in a way that triggers an error in the server's SSL_accept function. NOTE: the netkit ftp issue is covered by CVE-2007-5769.
CWE-20 - Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.