The IPv6 implementation in the Linux kernel before 3.1 does not generate Fragment Identification values separately for each destination, which makes it easier for remote attackers to cause a denial of service (disrupted networking) by predicting these values and sending crafted packets.
https://github.com/torvalds/linux/commit/87c48fa3b4630905f98268dde838ee43626a060c
https://bugzilla.redhat.com/show_bug.cgi?id=723429
http://www.securitytracker.com/id?1027274
http://www.openwall.com/lists/oss-security/2011/07/20/5