The remote host is missing an update to the system as announced in the referenced advisory FreeBSD-SA-08:10.nd6.asc

Upgrade your system to the appropriate stable release or security branch dated after the correction date https://secure1.securityspace.com/smysecure/catid.html?in=FreeBSD-SA-08:10.nd6.asc

IPv6 nodes use the Neighbor Discovery protocol to determine the link-layer address of other nodes, find routers, and maintain reachability information. The Neighbor Discovery protocol uses Neighbor Solicitation (ICMPv6 type 135) to query target nodes for their link-layer addresses. IPv6 routers may allow on-link IPv6 nodes to create and update the router's neighbor cache and forwarding information. A malicious IPv6 node sharing a common router but on a different physical segment from another node may be able to spoof Neighbor Discovery messages, allowing it to update router information for the victim node.