Oracle 8i and 9i with PL/SQL package for External Procedures (EXTPROC) allows remote attackers to bypass authentication and execute arbitrary functions by using the TNS Listener to directly connect to the EXTPROC process.
https://exchange.xforce.ibmcloud.com/vulnerabilities/8089
http://www.securityfocus.com/bid/4033
http://www.kb.cert.org/vuls/id/180147
http://www.cert.org/advisories/CA-2002-08.html
http://otn.oracle.com/deploy/security/pdf/plsextproc_alert.pdf