The audit facility in the Security component in IBM DB2 UDB 9.5 before FP6a uses instance-level audit settings to capture connection (aka CONNECT and AUTHENTICATION) events in certain circumstances in which database-level audit settings were intended, which might make it easier for remote attackers to connect without discovery.
CWE-287 - Improper Authentication
Improper (or broken) authentication attacks are widespread, and have accounted for many of the worst data breaches in recent years. Improper authentication attacks are a class of vulnerabilities where an attacker impersonates a legitimate user by exploiting weaknesses in either session management or credential management to gain access to the user’s account. This can result in disclosure of sensitive information, and can lead to system compromise, theft, identity theft, and fraud.