The Aastra 9112i SIP Phone with firmware 1.4.0.1048 and boot version 1.1.0.10 allows remote attackers to (1) cause a denial of service (device freeze) via a malformed SIP message of a certain length or (2) cause a denial of service (continuous ring) via a malformed SIP message of a certain other length.
https://exchange.xforce.ibmcloud.com/vulnerabilities/35060
http://www.vupen.com/english/advisories/2007/2318
http://www.sipera.com/index.php?action=resources%2Cthreat_advisory&tid=277&
http://www.securityfocus.com/bid/24537