CVE-2019-18792 Information

Description

An issue was discovered in Suricata 5.0.0. It is possible to bypass/evade any tcp based signature by overlapping a TCP segment with a fake FIN packet. The fake FIN packet is injected just before the PUSH ACK packet we want to bypass. The PUSH ACK packet (containing the data) will be ignored by Suricata because it overlaps the FIN packet (the sequence and ack number are identical in the two packets). The client will ignore the fake FIN packet because the ACK flag is not set. Both linux and windows clients are ignoring the injected packet.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Reference

https://github.com/OISF/suricata/commit/1c63d3905852f746ccde7e2585600b2199cefb4b https://github.com/OISF/suricata/commit/fa692df37a796c3330c81988d15ef1a219afc006 https://lists.debian.org/debian-lts-announce/2020/01/msg00032.html https://redmine.openinfosecfoundation.org/issues/3324 https://redmine.openinfosecfoundation.org/issues/3394

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

HIGH

Base Score

HIGH

Base Severity

9.1