TLP Rating: Clear 
CERT Vanuatu (CERTVU) and the Office of the Chief Information Officer (OGCIO) provide the following advisory.
On June 12th, 2023, CERT Vanuatu received an advisory from its collaborating partner, Cybersecurity Infrastructure Security Agency (CISA) that Fortinet has released security updates to address a heap-based buffer overflow vulnerability CVE-2023-27997.
What is it?
A remote Code Execution vulnerability (CVE-2023-27997) has been identified in multiple versions of Fortinet FortiGate devices when SSL=VPN enabled. An attacker could exploit this vulnerability to take control of an affected system.
Technical Details of CVE – 2023- 27997 – Fortinet Fortigate SSL VPN Pre-Auth TSC Vulnerability
Announced 12th of June 2023
Impact high/critical
Products FortiOS
The Vulnerability, CVE-2023-27997, is a heap-based buffer bug that allows unauthenticated remote code execution (RCE) on the affected system.
How Bad is It?
The vulnerability is very serious, as it can compromise the security and integrity of the network protected by Fortigate devices. Secure Channel can be compromised by attackers to execute arbitrary code or Commands on the device. This is referred to as the SSL VPN used for remote access to an organization's Network.
What should I do to Stay Safe?
Fortinet has issued patches for the vulnerability, which are included in Versions 7.2.5,
7.0.12, 6.4.13, 6.2.15, and 6.0.17 of FortiOS Firmware.
Users are strongly advised to update their systems to these versions as soon as possible to prevent potential attacks.
Users should review their network configurations and Firewall Rules to ensure that only authorized and trusted users can access the SSL VPN functionalities of FortiGate devices.
References
- https://www.cisa.gov/news-events/alerts/2023/06/12/fortinet-releases-security-updates-fortios-and-fortiproxy
- https://www.cyber.gov.au/about-us/view-all-content/alerts-and-advisories/critical-severity-vulnerability-fortinet-fortigate-ssl-vpn-devices
- https://www.fortinet.com/blog/psirt-blogs/analysis-of-cve-2023-27997-and-clarifications-on-volt-typhoon-campaign
- https://www.blumira.com/cve-2023-27997/#:~:text=The%20vulnerability%2C%20CVE%2D2023%2D,Charles%20Fol%20(%40cfreal_)%20
- Download advisory (English): CVE – 2023- 27997 – Fortinet Fortigate SSL VPN Pre-Auth TSC Vulnerability
- Download advisory (French): Fortinet publie des mises à jour de sécurité pour FortiOS et FortiProxy
- Download advisory (Bislama): Fortinet i Rilisim ol Sekuriti Apdeit blong FortiOS mo FortiProxy