RNN Guestbook's gbadmin.cgi script only asks for authentication when attempting to access the main admin page. If an attacker provides a specific QUERY_STRING with the gbadmin.cgi request, the script will not require authentication. This allows a remote attacker to have full administrative control over the guestbook system.
Classification
Unknown or Incomplete
Solution
Currently, there are no known upgrades or patches to correct this issue. It is possible to correct the flaw by disabling all access to the guestbook scripts until a patch or upgrade is made available.