The bgp_capability_orf function in bgpd in Quagga 0.99.20.1 and earlier allows remote attackers to cause a denial of service (assertion failure and daemon exit) by leveraging a BGP peering relationship and sending a malformed Outbound Route Filtering (ORF) capability TLV in an OPEN message.
http://rhn.redhat.com/errata/RHSA-2012-1259.html
http://secunia.com/advisories/50941
http://www.debian.org/security/2012/dsa-2497