The BGP implementation in bgpd in Quagga before 0.99.20.1 does not properly use message buffers for OPEN messages, which allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a message associated with a malformed Four-octet AS Number Capability (aka AS4 capability).
http://www.kb.cert.org/vuls/id/551715
http://www.debian.org/security/2012/dsa-2459
http://secunia.com/advisories/48949
http://rhn.redhat.com/errata/RHSA-2012-1259.html
http://lists.fedoraproject.org/pipermail/package-announce/2012-April/078926.html
http://lists.fedoraproject.org/pipermail/package-announce/2012-April/078910.html
http://lists.fedoraproject.org/pipermail/package-announce/2012-April/078794.html