tnftp is a NetBSD FTP client with several advanced features.
The 'mget' function in cmds.c lacks validation of the filenames that are supplied by the server.
An attacker running an FTP server could supply clients with malicious filenames, potentially allowing the overwriting of arbitrary files with the permission of the connected user.
There is no known workaround at this time.
All tnftp users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-ftp/tnftp-20050103"