An issue was discovered in ytnef before 1.9.1. This is related to a patch described as "3 of 9. Buffer Overflow in version field in lib/tnef-types.h."
https://www.x41-dsec.de/lab/advisories/x41-2017-002-ytnef/
https://github.com/Yeraze/ytnef/pull/27
http://www.securityfocus.com/bid/96423