An issue was discovered in tnef before 1.4.13. Several Integer Overflows, which can lead to Heap Overflows, have been identified in the functions that wrap memory allocation.
https://www.x41-dsec.de/lab/advisories/x41-2017-004-tnef/
https://security.gentoo.org/glsa/201708-02
https://github.com/verdammelt/tnef/commit/c5044689e50039635e7700fe2472fd632ac77176
https://github.com/verdammelt/tnef/blob/master/ChangeLog