FreeBSD -- TCP MD5 signature denial of service

Problem Description:
A programming error in processing a TCP connection with
both TCP_MD5SIG and TCP_NOOPT socket options may lead to
kernel crash.
Impact:
A local attacker can crash the kernel, resulting in a
denial-of-service.
A remote attack is theoretically possible, if server has
a listening socket with TCP_NOOPT set, and server is either
out of SYN cache entries, or SYN cache is disabled by
configuration.