Hackers are exploiting a new Fortinet firewall bug to breach company networks

**Executive summary:** Security researchers and Fortinet confirm a critical FortiGate vulnerability (CVE-2024-55591) is being exploited in the wild as a zero-day; Arctic Wolf observed a mass exploitation campaign against internet-exposed management interfaces since December, Fortinet released patches and CISA urged customers to update, and analysts warn ransomware operators may be exploiting the bug.