FreeBSD -- Resource exhaustion in TCP reassembly

Problem Description:
One of the data structures that holds TCP segments uses
an inefficient algorithm to reassemble the data. This causes
the CPU time spent on segment processing to grow linearly
with the number of segments in the reassembly queue.
Impact:
An attacker who has the ability to send TCP traffic to
a victim system can degrade the victim system’s network
performance and/or consume excessive CPU by exploiting the
inefficiency of TCP reassembly handling, with relatively
small bandwidth cost.