Suricata before 5.0.8 and 6.x before 6.0.4 allows TCP evasion via a client with a crafted TCP/IP stack that can send a certain sequence of segments.
https://redmine.openinfosecfoundation.org/issues/4569
https://github.com/OISF/suricata/releases
https://forum.suricata.io/t/suricata-6-0-4-and-5-0-8-released/1942