CVE-2025-25249

CVE-2025-25249 is a heap-based buffer overflow (CWE-122/CWE-787) in Fortinet FortiOS, FortiSwitchManager, and FortiSASE that allows an attacker to execute unauthorized code or commands. It is triggered by sending specially crafted packets to an affected device, causing an out-of-bounds write in heap memory that can be leveraged for code execution. Successful exploitation gives attackers command execution on the appliance; in observed intrusions against FortiGate firewalls, attackers have deployed custom Node.js malware and a post-exploitation RAT dubbed PivotC2. Any organization running the affected Fortinet products is at risk, with internet-facing FortiGate firewalls the primary concern. The flaw was added to CISA's KEV on 2026-09-09, confirming active exploitation in the wild (ransomware use unknown); no public PoC is known.

What to do: Upgrade FortiOS, FortiSwitchManager, and FortiSASE in accordance with Fortinet's advisory (specific fixed versions are not listed in the available data), prioritizing internet-exposed FortiGate firewalls per CISA KEV and BOD 26-04 timelines. Hunt for signs of compromise, including custom Node.js malware and the PivotC2 RAT, on FortiGate devices, and review exposure and access logs for admin/SSL-VPN interfaces. If patching is not possible, apply vendor-recommended mitigations or, per BOD 26-04, discontinue use of the exposed product.