In Suricata before 6.0.13, an adversary who controls an external source of Lua rules may be able to execute Lua code. This is addressed in 6.0.13 by disabling Lua unless allow-rules is true in the security lua configuration section.
An issue was discovered in Suricata before 6.0.4. It is possible to bypass/evade any HTTP-based signature by faking an RST TCP packet with random TCP options of the md5header from the client side. After the three-way handshake, it's possible to inject an RST ACK with a random TCP md5header option. Then, the client can send an HTTP GET request with a forbidden URL. The server will ignore the RST ACK and send the response HTTP packet for the client's request. These packets will not trigger a Suricata reject action.
Open Information Security Foundation Suricata prior to version 4.1.3 is affected by: Denial of Service - TCP/HTTP detection bypass. The impact is: An attacker can evade a signature detection with a specialy formed sequence of network packets. The component is: detect.c (https://github.com/OISF/suricata/pull/3625/commits/d8634daf74c882356659addb65fb142b738a186b). The attack vector is: An attacker can trigger the vulnerability by a specifically crafted network TCP session. The fixed version is: 4.1.3.