The remote host is missing an update to the system as announced in the referenced advisory FreeBSD-SA-04:04.tcp.asc

Upgrade your system to the appropriate stable release or security branch dated after the correction date https://secure1.securityspace.com/smysecure/catid.html?in=FreeBSD-SA-04:04.tcp.asc

The Transmission Control Protocol (TCP) of the TCP/IP protocol suite provides a connection-oriented, reliable, sequence-preserving data stream service. When network packets making up a TCP stream (``TCP segments'') are received out-of-sequence, they are maintained in a reassembly queue by the destination system until they can be re-ordered and re-assembled. FreeBSD does not limit the number of TCP segments that may be held in a reassembly queue.