A NULL pointer dereference vulnerability exists in the handling of the MXIT protocol in Pidgin. Specially crafted MXIT data sent via the server could potentially result in a denial of service vulnerability. A malicious server can send a packet starting with a NULL byte triggering the vulnerability.
https://security.gentoo.org/glsa/201701-38
http://www.ubuntu.com/usn/USN-3031-1
http://www.talosintelligence.com/reports/TALOS-2016-0137/
http://www.securityfocus.com/bid/91335