An incorrect group assignment (gid 0) occurs for domain users using the rfc2307 or sfu Winbind nss info plugin.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/59238/samba-gid0.txt
Source: https://packetstormsecurity.com/files/59238/samba-gid0.txt.html