05/04/2026
Fortinet has issued an emergency hotfix after security researchers disclosed a critical zero-day vulnerability in FortiClient EMS that is already being actively exploited by threat actors.
Tracked as CVE-2026-35616 and carrying a CVSSv3 score of 9.1 (Critical), the flaw enables unauthenticated attackers to bypass API authentication and authorization controls entirely, allowing them to execute arbitrary code or commands on vulnerable systems.
The vulnerability, classified under CWE-284 (Improper Access Control), resides in the API layer of FortiClient Endpoint Management Server (EMS).
Successful exploitation does not require any prior authentication, user interaction, or elevated privileges, making it particularly dangerous for organizations with internet-exposed EMS deployments.
An unauthenticated remote attacker can send specially crafted API requests to bypass all authentication and authorization checks, effectively gaining full control over endpoint management operations.
The attack vector is network-based, the complexity is low, and the impact spans confidentiality, integrity, and availability conditions that directly account for its near-maximum CVSS rating.
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Fortinet has issued an emergency hotfix after security researchers disclosed a critical zero-day vulnerability in FortiClient EMS that is already being actively exploited by threat actors.