Security researchers have identified that hackers are exploiting a critical vulnerability, tracked as CVE-2024-55591, in Fortinet's FortiGate firewalls to infiltrate corporate networks. Fortinet confirmed the ongoing exploitation in an advisory, revealing that patches were released after the issue was already being exploited as a zero-day since December. Cybersecurity firm Arctic Wolf reported a significant number of intrusions linked to this vulnerability. While the exact number of affected customers remains unclear, Fortinet has urged users to update devices promptly to mitigate risks. Ransomware operators may be behind these attacks, raising alarms within the cybersecurity community.