The Telnet service for Polycom ViewStation before 7.2.4 does not restrict the number of failed login attempts, which makes it easier for remote attackers to guess usernames and passwords via a brute force attack.
https://exchange.xforce.ibmcloud.com/vulnerabilities/44241
http://www.polycom.com/common/pw_item_show_doc/0%2C%2C1444%2C00.pdf