Nmap 5.61 TEST2 – IPv6 OS detection, CPE, 30 more scripts, and more features in latest release. The database is still very small, so please submit anyfingerprints that Nmap gives you to the specified URL. The new system utilizes many tests similar to IPv4, and also some IPv6-specific ones that we found to be particularly effective. We hope to move some of the IPv6 innovations back to our IPv4 system if they work out well.
Source: https://thehackernews.com/2011/09/nmap-561-test2-ipv6-os-detection-added.html