The vulnerability manifests in the SASL authentication flow when handling client responses. The core issue is in PlainSaslServer's response evaluation method:

1. The JIRA ticket QPID-7271 explicitly mentions fixing exception handling in PlainSaslServer
2. SASL mechanisms in Java typically implement evaluateResponse() for authentication processing
3. The vulnerability description specifies uncaught exceptions during authentication attempts
4. The plaintext authentication mechanism would split client input into username/password components using null byte separators - a process vulnerable to malformed inputs
5. Pre-patch versions lack proper try-catch blocks around this parsing logic, letting runtime exceptions propagate to the JVM
6. The patched version (6.0.3) adds explicit SaslException handling as seen in the JIRA resolution comment