BitlBee before 3.5 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) and possibly execute arbitrary code via a file transfer request for a contact that is not in the contact list.
https://github.com/bitlbee/bitlbee/commit/701ab8129ba9ea64f569daedca9a8603abad740f
https://bugs.bitlbee.org/ticket/1282
http://www.securityfocus.com/bid/95931
http://www.openwall.com/lists/oss-security/2017/01/31/11