The Winbind nss_info extension (nsswitch/idmap_ad.c) in idmap_ad.so in Samba 3.0.25 through 3.0.25c, when the "winbind nss info" option is set to rfc2307 or sfu, grants all local users the privileges of gid 0 when the (1) RFC2307 or (2) Services for UNIX (SFU) primary group attribute is not defined.