Stack Buffer Overflow in VMware HGFS Host-Guest Communication

CVE-2026-59347 is a stack-based buffer overflow vulnerability affecting VMware Workstation and Fusion versions 25H2 and 26H1, with a fix available in 26H1u1. This vulnerability exists in the Host Guest File System (HGFS) component that handles file sharing between host and guest virtual machines. An attacker with local administrative privileges on a guest VM can exploit this flaw to execute arbitrary code within the VMX process—the virtualization engine running on the host system. This represents a critical privilege escalation path: compromising a guest VM's admin account becomes a vector for breaking out to the host hypervisor, potentially affecting all VMs on that host and the underlying infrastructure.

While CVE-2026-59347 does not currently map to MITRE ATT&CK techniques in threat intelligence databases, Casky's approach using Claude AI with extended reasoning capabilities would detect exploitation attempts by analyzing the behavioral signatures associated with CWE-121 stack buffer overflows. Practitioners leveraging Casky would identify attack patterns including anomalous HGFS inter-process communication (IPC) with oversized payloads, unexpected memory access patterns in the VMX process, attempts to trigger HGFS file-sharing operations with crafted input, and post-exploitation indicators such as elevated process spawning from VMX. By mapping behavioral indicators to the underlying vulnerability mechanics, security teams can detect exploitation attempts even as attackers refine their techniques, enabling proactive threat hunting and rapid incident response before host-level compromise occurs.