many out-of-sequence TCP packets denial-of-service

FreeBSD does not limit the number of TCP segments that may be held in a reassembly queue. A remote attacker may conduct a low-bandwidth denial-of-service attack against a machine providing services based on TCP (there are many such services, including HTTP, SMTP, and FTP). By sending many out-of-sequence TCP segments, the attacker can cause the target machine to consume all available memory buffers (``mbufs''), likely leading to a system crash.