CVE-2023-20869: VMware Fusion Buffer Overflow Vulnerability

CVE-2023-20869 Overview

CVE-2023-20869 is a stack-based buffer overflow vulnerability affecting VMware Workstation (17.x) and VMware Fusion (13.x). The vulnerability exists in the functionality for sharing host Bluetooth devices with the virtual machine, allowing a malicious actor with local administrative privileges on a virtual machine to execute code as the virtual machine's VMX process running on the host.

Critical Impact

A local attacker with high privileges can exploit this stack-based buffer overflow in the Bluetooth device sharing functionality to execute arbitrary code on the host system, potentially leading to a complete VM escape scenario.

Affected Products

• VMware Workstation 17.x
• VMware Fusion 13.x

Discovery Timeline

• 2023-04-25 - CVE-2023-20869 published to NVD
• 2025-02-04 - Last updated in NVD database

Technical Details for CVE-2023-20869

Vulnerability Analysis

This stack-based buffer overflow vulnerability (CWE-787: Out-of-bounds Write) resides in VMware's Bluetooth device sharing functionality, which allows virtual machines to access Bluetooth devices connected to the host system. The vulnerability can be triggered when processing Bluetooth-related data passed from the guest VM to the host.

Successful exploitation requires local access and high privileges within the virtual machine. However, once exploited, the attacker can execute code as the VMX process on the host, effectively escaping the VM sandbox. The scope changes from the virtual machine context to the host system, resulting in potential compromise of confidentiality, integrity, and availability of the host.

Root Cause

The vulnerability stems from improper bounds checking when handling Bluetooth device data in the shared device functionality. When a virtual machine sends specially crafted Bluetooth-related requests to the host through the device sharing mechanism, the VMware hypervisor fails to properly validate the size of input data before copying it to a stack-allocated buffer. This allows an attacker to overflow the buffer and overwrite adjacent stack memory, including return addresses or function pointers.

Attack Vector

The attack requires local access to a virtual machine running on a vulnerable VMware Workstation or Fusion installation. An attacker with administrative privileges on the guest VM can craft malicious Bluetooth device sharing requests that trigger the buffer overflow. By carefully controlling the overflow data, the attacker can achieve code execution in the context of the VMX process on the host system.

The exploitation path involves:

1. Gaining administrative access to a guest virtual machine
2. Enabling or utilizing the Bluetooth device sharing feature
3. Sending specially crafted data through the Bluetooth sharing interface
4. Triggering the stack buffer overflow in the VMX process
5. Executing arbitrary code on the host system with VMX process privileges

Detection Methods for CVE-2023-20869

Indicators of Compromise

• Unusual Bluetooth-related activity or traffic between guest VMs and the host
• Unexpected crashes or restarts of VMware Workstation or Fusion processes
• Anomalous VMX process behavior, including spawning unexpected child processes
• Evidence of code execution attempts from within virtual machine contexts

Detection Strategies

• Monitor VMware process logs for abnormal Bluetooth device sharing operations
• Implement endpoint detection to identify stack buffer overflow exploitation attempts
• Use SentinelOne's behavioral AI to detect anomalous VMX process activity
• Deploy memory protection solutions that can detect stack-based exploitation techniques

Monitoring Recommendations

• Enable detailed logging for VMware Workstation and Fusion Bluetooth operations
• Implement host-based intrusion detection to monitor VM-to-host communication channels
• Configure alerts for unexpected privilege escalation or VM escape attempts
• Regularly audit virtual machine configurations for unnecessary device sharing features

How to Mitigate CVE-2023-20869

Immediate Actions Required

• Update VMware Workstation to version 17.0.2 or later
• Update VMware Fusion to version 13.0.2 or later
• Disable Bluetooth device sharing on all virtual machines until patches are applied
• Review and restrict virtual machine administrative access to trusted users only

Patch Information

VMware has released security updates to address this vulnerability. Detailed patch information is available in the VMware Security Advisory VMSA-2023-0008. Organizations should prioritize applying these patches, especially in environments where virtual machines may be accessible to untrusted users.

Workarounds

• Turn off the Bluetooth device sharing feature on affected virtual machines by editing the VM configuration
• Restrict access to virtual machines to only trusted administrators
• Implement network segmentation to limit potential lateral movement if exploitation occurs
• Consider disabling all unnecessary virtual device sharing features until patches can be applied

# Disable Bluetooth device sharing in VMware configuration
# Add or modify the following line in the .vmx file:
usb.autoConnect.bluetooth = "FALSE"

# Verify Bluetooth sharing is disabled
grep -i bluetooth /path/to/vm.vmx