FreeBSD Security Advisory – There is no mechanism for preventing IPv6 routing headers from being used to route packets over the same link(s) many times. An attacker can “amplify” a denial of service attack against a link between two vulnerable hosts; that is, by sending a small volume of traffic the attacker can consume a much larger amount of bandwidth between the two vulnerable hosts. An attacker can use vulnerable hosts to “concentrate” a denial of service attack against a victim host or network; that is, a set of packets sent over a period of 30 seconds or more could be constructed such that they all arrive at the victim within a period of 1 second or less.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/56342/FreeBSD-SA-07-03-ipv6.txt
Source: https://packetstormsecurity.com/files/56342/FreeBSD-SA-07-03-ipv6.txt.html