Florian Weimer of the Red Hat Product Security Team discovere that the mnl_nlmsg_portid_ok() function in libmnl 1.0.3 and earlier did not correctly validate the origin of a Netlink message, allowing local attackers to spoof Netlink messages, with context-dependent consequences.
This is currently being discussed here: http://marc.info/?l=linux-netdev&m=134522422125983 but in the capacity of the kernel, not libmnl.
This was fixed in the kernel, see bug 851968.