CVE-2023-40718: IPS Engine evasion using custom TCP flags

Q: What is CVE-2023-40718?

CVE-2023-40718 is a vulnerability in Fortinet IPS Engine versions 7.321, 7.166, and 6.158 that allows attackers to evade IPS features through crafted TCP packets.

Q: How can an attacker exploit CVE-2023-40718?

An attacker can exploit CVE-2023-40718 by sending specially crafted TCP packets to evade IPS features.

Q: Which versions of Fortinet IPS Engine are affected by CVE-2023-40718?

Fortinet IPS Engine versions 7.321, 7.166, and 6.158 are affected by CVE-2023-40718.

Q: What is the severity of CVE-2023-40718?

CVE-2023-40718 has a severity rating of 7.5 (High).

Q: Where can I find more information about CVE-2023-40718?

More information about CVE-2023-40718 can be found at https://fortiguard.com/psirt/FG-IR-23-090.

Published Oct 10, 2023

Updated

A interpretation conflict in Fortinet IPS Engine versions 7.321, 7.166 and 6.158 allows attacker to evade IPS features via crafted TCP packets.

Other sources

An interpretation conflict vulnerability [CWE-436] in FortiOS IPS Engine may allow an unauthenticated remote attacker to evade NGFW policies or IPS Engine protection via crafted TCP packets.

— FortiGuard

Affected Software

6 affected components

Fortinet FortiOS IPS Engine<=7.312

Fortinet FortiOS>=7.2.0<7.2.4

Fortinet FortiOS IPS Engine<=7.165

Fortinet FortiOS>=7.0.0<7.0.12

Fortinet FortiOS IPS Engine<=6.158

Fortinet FortiOS>=6.4.0<6.4.13

Remediation

Information

IPS Engine manual download is not needed unless device is offline and cannot download IPS Engine update automatically. Fixed in IPS Engine version 6.0159 and later. FortiOS 6.4.13 and later contains IPS engine 6.0160 as the default IPS Engine. IPS Engine 6.0162 is downloadable from FortiGuard by FortiGate units with a valid subscription running FortiOS 6.4.x. Fixed in IPS Engine version 7.0166 and later. FortiOS 7.0.12 and later contains IPS engine 7.0167 as the default IPS Engine. Fixed in IPS Engine version 7.0313 and later. FortiOS 7.2.5 and later contains IPS engine 7.0314 as the default IPS Engine. IPS Engine 7.0322 is downloadable from FortiGuard by FortiGate units with a valid subscription running FortiOS 7.2.x. FortiOS 7.4.0 and later contains IPS engine 7.0493 as the default IPS Engine.

Event History

Oct 10, 2023

Advisory Published

via FortiGuard·12:00 AM

Data Sourced

via FortiGuard·12:00 AM

DescriptionSeverityWeaknessAffected Software

CVE Published

via MITRE·04:49 PM

Data Sourced

via MITRE·04:49 PM

RemedyDescriptionSeverityWeakness

Oct 25, 2024

Advisory Published

via FortiGuard·11:28 PM

Frequently Asked Questions

What is CVE-2023-40718?