Critical FortiClient EMS Vulnerability Exploited in Fresh Attacks

CVE-2026-35616 in FortiClient Endpoint Management Server enables remote code execution through crafted requests without authentication. Hotfixes were released in early April after Fortinet warned the flaw was exploited in the wild as a zero-day. Unpatched deployments are being targeted in a campaign that deploys EKZ Infostealer disguised as a fake Fortinet endpoint patch. The malware is executed through FortiClient-managed VPN scripting workflows using command scripts that invoke PowerShell, indicating familiarity with the environment. Compromise of the central EMS appliance enables code execution across all managed endpoints. EKZ Infostealer targets Chrome, Microsoft Edge, Firefox, and other Chromium and Gecko-based browsers to steal credentials, cookies, and autofill data, then exfiltrates harvested data over HTTP.

"The flaw, tracked as CVE-2026-35616 (CVSS score of 9.1), can be exploited remotely via crafted requests for remote code execution (RCE) and does not require authentication. Fortinet rolled out hotfixes for the security defect in early April, warning that it had been exploited in the wild as a zero-day and urging immediate patching."

"Unpatched FortiClient EMS deployments are now being targeted in a campaign deploying the EKZ Infostealer disguised as a fake Fortinet endpoint patch. The payload was executed via FortiClient-managed VPN scripting workflows, using command scripts that invoked PowerShell, suggesting knowledge of the affected environment."

""The observed execution pattern suggests that threat actors used FortiClient's own management pathway to push malicious PowerShell commands to managed endpoints in a way that resembled legitimate management operations," Arctic Wolf says. Because FortiClient EMS functions as a central management platform for FortiClient devices, policies, and configurations, access to the appliance enabled the attackers to execute code on every managed endpoint, the cybersecurity firm notes."

"The information-stealing malware deployed in these attacks targets Chrome, Microsoft Edge, Firefox, and other Chromium and Gecko-based browsers for credential, cookie, and autofill data theft. The harvested data is exfiltrated over HTTP. "The application does not possess network-based credentials exfiltration capabilities; instead, it exports credentials from supported browsers to an output log file. Run without arguments, it provides command-line usage details," Arctic Wolf notes."

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