nfnetlink_log in netfilter in the Linux kernel before 2.6.20.3 allows attackers to cause a denial of service (crash) via unspecified vectors involving the (1) nfulnl_recv_config function, (2) using "multiple packets per netlink message", and (3) bridged packets, which trigger a NULL pointer dereference.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9831
http://www.vupen.com/english/advisories/2007/0944
http://www.ubuntu.com/usn/usn-464-1
http://www.securityfocus.com/bid/22946
http://www.redhat.com/support/errata/RHSA-2007-0347.html
http://www.novell.com/linux/security/advisories/2007_43_kernel.html
http://www.mandriva.com/security/advisories?name=MDKSA-2007:171
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.20.3
http://www.debian.org/security/2007/dsa-1289
http://secunia.com/advisories/26620
http://secunia.com/advisories/25961
http://secunia.com/advisories/25392
http://secunia.com/advisories/25288