Oracle Database Server Network Denial Of Service

Sending a specially crafted network packet to an Oracle Database during the connection before the user authentication is performed it is possible to make the Oracle process consume all available CPU resources. To exploit this vulnerability no authentication is needed, the attacker needs to know the SID or Service Name of the database. Affected are Oracle Database Server versions 10gR1, 10gR2, 11gR1 and 11gR2 (on Windows platform).

Source: Oracle Database Server Network Denial Of Service