Windows NT 4.0 before SP3 allows remote attackers to bypass firewall restrictions or cause a denial of service (crash) by sending improperly fragmented IP packets without the first fragment, which the TCP/IP stack incorrectly reassembles into a valid session.
Windows NT 4.0 SP2 allows remote attackers to cause a denial of service (crash), possibly via malformed inputs or packets, such as those generated by a Linux smbmount command that was compiled on the Linux 2.0.29 kernel but executed on Linux 2.0.25.