An issue was discovered in Asterisk through 13.19.1, 14.x through 14.7.5, and 15.x through 15.2.1, and Certified Asterisk through 13.18-cert2. res_pjsip allows remote authenticated users to crash Asterisk (segmentation fault) by sending a number of SIP INVITE messages on a TCP or TLS connection and then suddenly closing the connection.
https://www.exploit-db.com/exploits/44181/
https://www.debian.org/security/2018/dsa-4320
https://issues.asterisk.org/jira/browse/ASTERISK-27618
http://www.securitytracker.com/id/1040417
http://www.securityfocus.com/bid/103129
http://downloads.asterisk.org/pub/security/AST-2018-005.html