VMware Fusion and Workstation 26H1u1 Fix Two Guest-to-Host Flaws
A virtual machine is useful partly because a compromised guest should not control the host. Preserving that boundary matters during everyday work.
Broadcom’s VMSA-2026-0007 covers VMware Workstation and Fusion 25H2 and 26H1. 26H1u1 is the fixed release for both, and the advisory lists no workaround. The VMXNET3 flaw, CVE-2026-59346, requires local administrative privileges in a guest configured with that adapter and could allow code execution on the host. The separate HGFS flaw, CVE-2026-59347, requires guest administrative privileges and could run code as that guest’s VMX process on the host. Broadcom’s matrix does not list ESXi or vSphere.
Development and analysis teams may deliberately run untrusted material inside a VM. For them, the containment boundary is part of the security model.
Which VMware builds need the update?
| Product | Affected releases | Fixed release | Workaround |
|---|---|---|---|
| VMware Workstation | 25H2 and 26H1 | 26H1u1 | None listed |
| VMware Fusion | 25H2 and 26H1 on macOS | 26H1u1 | None listed |
Inventory host builds and rank them by guest workload and exposed credentials.
Assess host-side exposure
Source code, signing or cloud credentials, local analysis tools and other VMs may sit nearby. Identify hosts that process hostile samples before treating the update as a routine desktop-app refresh.
Review file sharing separately
Shared folders connect guest and host files.
Broadcom does not report observed malicious use. That omission is not proof of absence.
Assess who controls each guest
A guest can become administrator-controlled through a malicious installer, a vulnerable service, stolen credentials or an intentionally hostile test sample. For teams that assume a guest may be lost, the useful question is how much trust the host places in that guest’s virtual devices and convenience features.
Those conditions should inform inventory and exposure checks. They do not make the patch optional for teams whose security model assumes that even an untrusted guest remains contained.
Deploy and verify the update
Inventory hosts, deploy the vendor update and verify the installed build. Do not report a configuration change as an equivalent repair.
If the update cannot be immediate, reduce the opportunity for a hostile guest to interact with valuable host material. Limit untrusted workloads and host credentials on those machines and review whether shared folders are necessary. These are risk-reduction choices, not vendor fixes or proof that the virtualisation boundary is safe.
Treat unusual host behaviour as an investigation trigger under normal monitoring.
Test the dependent workflows
Verify the installed build, then test the workflows that depend on the guest. A disclosed fix cannot guarantee that every future escape has been eliminated.
Sources and further reading
- Broadcom VMSA-2026-0007, issued 3 September 2026.
