SCTP conntrack (ip_conntrack_proto_sctp.c) in netfilter for Linux kernel 2.6.17 before 2.6.17.3 and 2.6.16 before 2.6.16.23 allows remote attackers to cause a denial of service (crash) via a packet without any chunks, which causes a variable to contain an invalid value that is later used to dereference a pointer.