Description

Huntress’ Tactical Response Team has disclosed a highly advanced intrusion identified in December 2025 in which threat actors successfully performed a virtual machine (VM) escape, allowing them to gain full control of a VMware ESXi hypervisor. By breaking out of a guest VM, the attackers were able to compromise the underlying host and all workloads running on it, directly challenging the long-held assumption that virtualization provides strict isolation. The investigation indicates that the attack leveraged a sophisticated exploit toolkit that may have existed as a zero-day for more than a year prior to public disclosure. Rather than beginning with a hypervisor flaw, the intrusion started with a compromised SonicWall VPN account. Attackers then moved laterally from a backup domain controller to the primary controller before deploying a toolkit orchestrated by a binary known as MAESTRO. Once executed, MAESTRO disabled VMware drivers to enable direct hardware access and abused a Bring-Your-Own-Vulnerable-Driver (BYOVD) technique to load an unsigned malicious driver, MyDriver.sys, into the Windows kernel. This allowed the attackers to bypass security controls and escalate privileges, ultimately escaping the VMX sandbox. Following the VM escape, the attackers deployed a stealthy backdoor called VSOCKpuppet, which communicates using VSOCK (Virtual Sockets)—a host-guest interface not monitored by traditional network defenses. This approach enabled covert command-and-control activity that evaded standard detection mechanisms. Huntress also identified simplified Chinese development strings and code timestamps suggesting the exploit was operational as early as February 2024. The toolkit supports 155 ESXi builds across versions 5.1 through 8.0 and exploits vulnerabilities tracked as CVE-2025-22224, CVE-2025-22225, and CVE-2025-22226. Huntress urges organizations to aggressively patch ESXi systems, monitor hosts directly, and retire end-of-life deployments immediately.