Cisco Unity 2.x, 3.x, and 4.x, when integrated with Microsoft Exchange, has several hard coded usernames and passwords, which allows remote attackers to gain unauthorized access and change configuration settings or read outgoing or incoming e-mail messages.
https://exchange.xforce.ibmcloud.com/vulnerabilities/18489
http://www.securityfocus.com/bid/11954
http://www.cisco.com/warp/public/707/cisco-sa-20041215-unity.shtml