Inside VMSA-2025-0013: Critical Vulnerabilities in VMware ESXi, Workstation, Fusion, and Tools
Inside VMSA-2025-0013: Critical Vulnerabilities in VMware ESXi, Workstation, Fusion, and Tools
What is it?
On July 15, 2025, Broadcom released VMSA-2025-0013, disclosing multiple critical vulnerabilities impacting VMware ESXi, Workstation, Fusion, and VMware Tools. These issues include three memory safety flaws that may lead to code execution on the host system, and one information disclosure issue resulting from uninitialized memory usage in vSockets.
All four vulnerabilities were discovered through the Pwn2Own competition and responsibly reported to Broadcom. Patches are now available for all actively supported platforms. The affected components are widely deployed across enterprise, developer, and test environments. ESXi remains foundational to private cloud and on-prem hypervisor deployments, while Workstation and Fusion are common in lab, desktop, and DevSecOps workflows. VMware Tools is also broadly installed for guest OS integration and is embedded in nearly every virtual machine by default.
Why does it matter?
Each of these vulnerabilities carries serious implications depending on the deployment context. While exploitation requires local administrative access within a guest virtual machine, successful abuse of these flaws can lead to code execution on the host system. That violates the hypervisor isolation model and introduces significant lateral risk.
CVE-2025-41236: VMXNET3 Integer OverflowThis vulnerability carries a CVSSv3 base score of 9.3 and affects the VMXNET3 virtual network adapter. If the adapter is enabled on a guest, an attacker with administrative access inside the VM can exploit an integer overflow to execute code on the host. VMs not using VMXNET3 are unaffected.
CVE-2025-41237: VMCI Integer UnderflowThis flaw also scores 9.3 in most contexts and involves the Virtual Machine Communication Interface. It results in an out-of-bounds write that can allow an attacker inside the guest to execute code as the host-side VMX process. On ESXi, this remains sandboxed, but on Workstation or Fusion it could lead to full host compromise.
CVE-2025-41238: PVSCSI Heap OverflowThe paravirtualized SCSI controller is vulnerable to a heap overflow that allows out-of-bounds writes. In ESXi, this issue is exploitable only under unsupported configurations, but in Workstation and Fusion it can again lead to host code execution from inside a VM.
CVE-2025-41239: vSockets Memory DisclosureThis information disclosure vulnerability is rated at 7.1 and affects ESXi, Workstation, Fusion, and VMware Tools. It stems from uninitialized memory usage in vSockets and can be used by a guest to leak data from host processes. While it does not lead to direct code execution, it weakens isolation and may assist in chaining more severe attacks.
The scope of these flaws reaches into core infrastructure. All are locally exploitable but carry disproportionate risk in environments where trust boundaries between guest and host must be maintained.
Risk Scenarios
These vulnerabilities are particularly concerning in scenarios where virtualization is nested or shared. In developer or security research environments, users often spin up untrusted workloads inside VMs on Fusion or Workstation. In these cases, a malicious guest may compromise the local machine entirely.
In enterprise ESXi deployments, attackers who obtain administrative access to a guest may use one of these flaws to execute code in the host context. From there, lateral movement, data exfiltration, or full infrastructure takeover become viable.
Even the Tools-specific memory leak presents risk when sensitive data resides in memory near vSockets communication channels. It may expose inter-process communications or leak authentication material in certain configurations.
In short, a vulnerable guest with root access can become a stepping stone to broader compromise, especially in environments where guests are treated as isolated or low-risk.
What can I do about it?
Patching is the only available mitigation. There are no workarounds, and the vulnerabilities affect default configurations on many systems.
Broadcom has released updated versions across all major product lines. Administrators should apply the following:
VMware ESXiUpdate to one of the following depending on your deployment version:
ESXi 8.0 U3f (Build 24784735)
ESXi 8.0 U2e (Build 24789317)
ESXi 7.0 U3w (Build 24784741)
VMware Workstation ProUpgrade to version 17.6.4
VMware FusionUpgrade to version 13.6.4
VMware Tools (Windows)Ensure version 13.0.1.0 or 12.5.3 is installed, particularly for 32-bit Windows guests. Linux and macOS guests are not affected.
Additional guidance is available in Broadcom’s FAQ, and asynchronous patching instructions for VMware Cloud Foundation deployments can be found in KB88287.
Conclusion: Bottom Line
VMSA-2025-0013 highlights a recurring theme in virtualization security. Privileged users inside guest VMs can, under the right conditions, escape their sandbox and reach the host layer. When flaws are present in network adapters, disk controllers, or interprocess communication channels, those boundaries erode quickly.
Enterprise and developer environments alike must treat this advisory with urgency. ESXi hosts underpin mission-critical workloads and require timely patching to ensure tenant separation. Fusion and Workstation users, especially those experimenting with untrusted VMs or malware samples, should treat this as a priority update.
One unpatched virtual machine can become the starting point for a far broader compromise. Mitigation begins with swift patch deployment and clear visibility into virtualization risk posture.
References
· Broadcom VMSA-2025-0013 Advisory
· VMware Fusion 13.6.4 Release Notes
· VMware Workstation 17.6.4 Release Notes