Arctic Wolf has observed active exploitation of CVE-2026-35616, an authentication-bypass flaw in FortiClient Enterprise Management Server (EMS), to deliver an undocumented credential stealer called EKZ. Attackers abuse the endpoint APIs to perform administrative actions without authentication, then modify EMS configuration and VPN policies to inject malicious scripts. Seconds after endpoints establish an IPsec tunnel to a Fortinet-managed gateway, EKZ is pushed disguised as an endpoint update via VPN scripting workflows. Fortinet released emergency hotfixes for versions 7.4.5 and 7.4.6 in early April and CISA ordered federal agencies to patch the same week; Shadowserver tracked 2,000 internet-exposed EMS instances at the time.
If you patched FortiClient EMS for CVE-2026-21643 two weeks ago by upgrading to 7.4.5, you're now vulnerable to a new zero-day. CVE-2026-35616 is a CVSS 9.1 pre-authentication API access bypass affecting versions 7.4.5 and 7.4.6 - the exact versions customers upgraded to. Defused Cyber spotted exploitation in the wild starting March 31. Fortinet released an emergency weekend hotfix on Saturday, with watchTowr noting attackers deliberately timed this for the Easter holiday when security teams are at half strength.
A CVSS 9.1 SQL injection flaw in Fortinet's FortiClient Endpoint Management Server is now being exploited in the wild - four days before anyone flagged it publicly. An attacker only needs one crafted HTTP request with a malicious Site header to execute arbitrary SQL against the backing PostgreSQL database, no credentials required. Roughly 1,000 to 2,400 FortiClient EMS instances are exposed to the internet, mostly in the US and Europe.
TrustStrike Labs