Critical FortiOS & FortiProxy – Heap buffer overflow Vulnerability

Critical FortiOS – FG-IR-23-097: Fortinet released security updates to address a heap-based buffer overflow vulnerability [CVE-2023-27997] in FortiOS. An attacker could exploit this vulnerability to take control of an affected system. Hackers are actively exploiting the latest Fortinet’s FortiOS and FortiProxy flaw, targeting government, manufacturing, and critical infrastructure sectors. Take immediate action and update to the latest firmware now!


Yesterday, Fortinet published a CVSS Critical PSIRT Advisory (FG-IR-23-097 / CVE-2023-27997) along with several other SSL-VPN related fixes. This blog adds context to that advisory, providing Forti customers with additional details to help them make informed, risk-based decisions, and provides their perspective relative to recent events involving malicious actor activity.

The highest severity issue fixed in this release is CRITICAL.

This vulnerability has a CVSS higher than 9. It’s already patched in the latest versions of FortiOS. Still, it’s not mentioned in their release notes. And the related PSIRT advisory from FortiGuardLabs is now publicly accessible. Fortinet is not aware of any instance where this vulnerability was exploited in the wild.


IR Number: FG-IR-23-097
Date: June 12, 2023
CVSSv3 Score: 9.2
Impact: Execute unauthorized code or commands
CVE ID: CVE-2023-27997

Recommended Actions:

In addition to monitoring Security Advisories and the immediate patching of systems, Fortinet strongly recommends the following:

  • Review your systems for evidence of exploit of previous vulnerabilities: FG-IR-22-377 / CVE-2022-40684,
  • Maintain good cyber hygiene and follow vendor patching recommendations,
  • Follow hardening recommendations: FortiOS 7.2.0 Hardening Guide,
  • Minimize the attack surface by disabling unused features and managing devices via an out-of-band method wherever possible.


Affected Products:
At least
FortiOS-6K7K version 7.0.10
FortiOS-6K7K version 7.0.5
FortiOS-6K7K version 6.4.12
FortiOS-6K7K version 6.4.10
FortiOS-6K7K version 6.4.8
FortiOS-6K7K version 6.4.6
FortiOS-6K7K version 6.4.2
FortiOS-6K7K version 6.2.9 through 6.2.13
FortiOS-6K7K version 6.2.6 through 6.2.7
FortiOS-6K7K version 6.2.4
FortiOS-6K7K version 6.0.12 through 6.0.16
FortiOS-6K7K version 6.0.10
At least
FortiProxy version 7.2.0 through 7.2.3
FortiProxy version 7.0.0 through 7.0.9
FortiProxy version 2.0.0 through 2.0.12
FortiProxy 1.2 all versions
FortiProxy 1.1 all versions
At least
FortiOS version 7.2.0 through 7.2.4
FortiOS version 7.0.0 through 7.0.11
FortiOS version 6.4.0 through 6.4.12
FortiOS version 6.2.0 through 6.2.13
FortiOS version 6.0.0 through 6.0.16


  • Please upgrade to FortiOS-6K7K version 7.0.12 or above,
  • Please upgrade to FortiOS-6K7K version 6.4.13 or above,
  • Please upgrade to FortiOS-6K7K version 6.2.15 or above,
  • Please upgrade to FortiOS-6K7K version 6.0.17 or above,
  • Please upgrade to FortiProxy version 7.2.4 or above,
  • Please upgrade to FortiProxy version 7.0.10 or above,
  • Please upgrade to FortiOS version 7.4.0 or above,
  • Please upgrade to FortiOS version 7.2.5 or above,
  • Please upgrade to FortiOS version 7.0.12 or above,
  • Please upgrade to FortiOS version 6.4.13 or above,
  • Please upgrade to FortiOS version 6.2.14 or above,
  • Please upgrade to FortiOS version 6.0.17 or above,


All users of Fortigate should use this time to inventory instances of Fortigate and prepare for immediate patching (patchs are already availables). We recommend that you begin identifying your vulnerable systems now and prepare to patch (schedule a Task Force especially) soon as possible.


Organizations, users, get ready! We’ll keep you updated.


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