IPv6 Extension Headers with Neighbor Discovery messages can be leveraged to circumvent simple local network protections, such as “Router Advertisement Guard”. Since there is no legitimate use for IPv6 Extension Headers in Neighbor Discovery messages, and such use greatly complicates network monitoring and simple security mitigations such as RA-Guard, this document proposes that hosts silently ignore Neighbor Discovery messages that use IPv6 Extension Headers.
You can download it from the following link: https://packetstormsecurity.com/files/download/119671/draft-ietf-6man-nd-extension-headers-03.txt
Source: https://packetstormsecurity.com/files/119671/Security-Implications-Of-IPv6-Fragmentation-With-IPv6-Neighbor-Discovery-Revision-03.html