A buffer overflow vulnerability exists in the handling of the MXIT protocol in Pidgin. Specially crafted MXIT data sent by the server could potentially result in an out-of-bounds write of one byte. A malicious server can send a negative content-length in response to a HTTP request triggering the vulnerability.
https://security.gentoo.org/glsa/201701-38
http://www.ubuntu.com/usn/USN-3031-1
http://www.talosintelligence.com/reports/TALOS-2016-0119/
http://www.securityfocus.com/bid/91335