The ProcessMimeEntity function in util-decode-mime.c in Suricata 4.x before 4.0.6 allows remote attackers to cause a denial of service (segfault and daemon crash) via crafted input to the SMTP parser, as exploited in the wild in November 2018.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.012
EPSS Ranking 78.1%