Fortinet Discloses Critical Vulnerability in FortiOS and FortiProxy SSL-VPN

On Monday, Fortinet disclosed a newly patched critical flaw that affects FortiOS and FortiProxy and which may have been exploited in a limited number of cases, targeting the government, manufacturing, and critical infrastructure sectors. This vulnerability is a heap-based buffer overflow vulnerability that could allow a remote attacker to execute arbitrary code or commands through a crafted request. Fortinet also disclosed that security researchers Charles Fol and Dany Bach from LEXFO discovered and reported the flaw.

Vulnerability Description: A heap-based buffer overflow in FortiOS and FortiProxy SSL-VPN

The vulnerability tracked as CVE-2023-27997 (CVSS score: 9.2) concerns a heap-based buffer overflow vulnerability in FortiOS and FortiProxy SSL-VPN. Attackers could exploit this vulnerability to execute arbitrary code or commands by sending a specifically crafted request. The flaw is a type of memory-based vulnerability that allows attackers to overwrite specific memory locations with malicious code. This malicious code is executed when the vulnerable application tries to access that memory location.

Discovery of Vulnerability: LEXFO Security Researchers Charles Fol and Dany Bach

LEXFO security researchers Charles Fol and Dany Bach have been credited with discovering and reporting the flaw. The researchers carry out vulnerability research to help security teams find vulnerabilities and enhance their security posture. LEXFO is a leading firm that provides offensive security research and development services.

Patch for the vulnerability was addressed by Fortinet on June 9, 2023

Fortinet addressed the vulnerability on June 9, 2021. The company provided patches that address the vulnerability. The patch is designed to address the flaw in FortiOS and FortiProxy SSL-VPN. Customers can install this patch to mitigate the risk of active exploitation.

Reason for Code Audit: Active Exploitation of a Similar Flaw in the SSL-VPN Product in December 2021

Fortinet initiated a code audit following the active exploitation of a similar flaw in the SSL-VPN product (CVE-2022-42475, CVSS score: 9.3) in December 2022. The analysis revealed that CVE-2023-27997 was also present in FortiOS and FortiProxy SSL-VPN at that time. Fortinet disclosed that the issue was simultaneously discovered during the audit that was prudently initiated.

Attribution of Exploitation Events: Fortinet does not attribute the exploitation events to a Chinese state-sponsored actor codenamed Volt Typhoon

Fortinet has not attributed the exploitation events to a Chinese state-sponsored actor codenamed Volt Typhoon. The company added that it continues to monitor the situation and proactively communicate with customers, urging them to follow guidance to mitigate the vulnerability.

Expectation of Further Exploitation: Fortinet Expects All Threat Actors to Continue Exploiting Unpatched Vulnerabilities in Widely Used Software and Devices

The company stated that it expects all threat actors, including those behind the Volt Typhoon campaign, to continue exploiting unpatched vulnerabilities in widely-used software and devices. Attacks are often opportunistic and seek high-value targets to achieve their objectives. This vulnerability can enable attackers to execute arbitrary code and steal sensitive information, posing a significant threat against organizations.

Action for Customers: Recommendation to update to the latest firmware version and avert potential risks

Fortinet recommends that customers take immediate action to update to the latest firmware version to avert potential risks. Updating the firmware is the best defense against this vulnerability, along with other good security practices such as maintaining up-to-date antivirus and firewalls, keeping systems and software patched, and training employees on the latest threats.

Continuous Monitoring and Communication: Fortinet continuously monitors the situation and proactively communicates with customers, urging them to follow guidance to mitigate the vulnerability

Fortinet continues to monitor the situation and has been proactively communicating with customers; strongly urging them to immediately follow the guidance provided to mitigate the vulnerability using either the provided workarounds or by upgrading. The company is committed to keeping customers informed of the situation and providing guidance to help mitigate the risk of exploitation.

The best defense against vulnerabilities is patching, up-to-date antivirus and firewalls, patched systems and software, and employee training against the latest threats

A patch is the best defense against this vulnerability, along with other good security practices such as maintaining up-to-date antivirus and firewalls, keeping systems and software patched, and training employees against the latest threats. Organizations should be aware of their security posture and have a plan in place to address vulnerabilities as soon as they are discovered. By implementing a security-first culture, organizations can help protect themselves from malicious actors seeking to exploit those vulnerabilities.

Fortinet has patched a critical vulnerability that could enable attackers to execute arbitrary code and commands in FortiOS and FortiProxy SSL-VPN. The company has urged customers to update their firmware and follow good security practices to mitigate the risk of exploitation. While Fortinet has not attributed the exploitation events to any specific adversary, the company expects all threat actors to continue exploiting unpatched vulnerabilities in widely used software and devices. Organizations should continuously monitor their security posture and have a plan in place to address vulnerabilities as soon as they are discovered.

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