Microsoft Security researchers have observed a vulnerability used by various ransomware operators to get full administrative access to domain-joined ESXi hypervisors and encrypt the virtual machines running on them. The vulnerability involves creating a group called “ESX Admins” in Active Directory and adding an attacker-controlled user account to this group. This manipulation of the Active Directory group takes advantage of a privilege escalation vulnerability (CVE-2024-37085) in ESXi hypervisors that grants the added user full administrative access to the ESXi hypervisor. The vulnerability was fixed by VMware in their June release and ESXi administrators should install this security update.