The process_rs function in the router advertisement daemon (radvd) before 1.8.2, when UnicastOnly is enabled, allows remote attackers to cause a denial of service (temporary service hang) via a large number of ND_ROUTER_SOLICIT requests.
http://www.ubuntu.com/usn/USN-1257-1
http://www.openwall.com/lists/oss-security/2011/10/06/3