Fortinet VPNs Under Attack: Potential Zero-Day Threats and How to Stay Safe

Fortinet users are being warned of potential cyberattacks targeting their endpoints through VPN tools. In early August 2025, researchers from GreyNoise detected a significant increase in brute-force attacks against Fortinet SSL VPN instances, where attackers attempt to guess passwords and authentication values.

Shortly after, similar attacks were observed against FortiManager, Fortinet’s centralized management platform. This activity raises concerns that attackers may be aware of a zero-day vulnerability in Fortinet products, as they map out potential targets and assess their importance within networks.

While no zero-day vulnerabilities have been confirmed, GreyNoise reports a high likelihood of one being exploited in the coming weeks. Historically, spikes in brute-force attacks have often preceded the disclosure of new vulnerabilities, with an 80% correlation observed in past cases.

To stay safe, users should remain vigilant against phishing attempts, especially unsolicited messages that demand urgent action or threaten dire consequences. These are key red flags in phishing attacks.

NPAV offers a robust solution to combat cyber fraud. Protect yourself with our top-tier security product, Z Plus Security