An issue was discovered in Teluu pjproject (pjlib and pjlib-util) in PJSIP before 2.7.1. The ioqueue component may issue a double key unregistration after an attacker initiates a socket connection with specific settings and sequences. Such double key unregistration will trigger an integer overflow, which may cause ioqueue backends to reject future key registrations.
https://www.debian.org/security/2018/dsa-4170