The sctp_new function in (1) ip_conntrack_proto_sctp.c and (2) nf_conntrack_proto_sctp.c in Netfilter in Linux kernel 2.6 before 2.6.20.13, and 2.6.21.x before 2.6.21.4, allows remote attackers to cause a denial of service by causing certain invalid states that trigger a NULL pointer dereference.