An issue was discovered in Asterisk Open Source 15.x before 15.4.1. When connected to Asterisk via TCP/TLS, if the client abruptly disconnects, or sends a specially crafted message, then Asterisk gets caught in an infinite loop while trying to read the data stream. This renders the system unusable.
https://issues.asterisk.org/jira/browse/ASTERISK-27807
http://www.securityfocus.com/bid/104457
http://downloads.asterisk.org/pub/security/AST-2018-007.html