The recently discovered CVE-2025-41237 in VMware’s virtualization platform is an integer-underflow vulnerability in VMCI (Virtual Machine Communication Interface) with a critical CVSSv3 score of 9.3. This vulnerability was first demonstrated at the Pwn2Own Berlin hacking contest in May 2025, and the official security advisory was released on July 15, requiring immediate response from VMware users worldwide.
This vulnerability enables VM escape attacks, allowing attackers with administrative privileges within a guest VM to execute code on the host system. While exploitation on ESXi is contained within the VMX sandbox, VMware Workstation and Fusion environments face complete host system exposure, making immediate patching essential.
1. Understanding CVE-2025-41237: Real Risks and Impact Scope
CVE-2025-41237 is an integer-underflow vulnerability in VMCI (Virtual Machine Communication Interface) that results in out-of-bounds writes. This isn’t just a simple security issue—it’s a critical threat that can break down the fundamental isolation boundaries of virtualized environments.
Affected Products and Versions
| Product | Affected Versions | Risk Level |
|---|---|---|
| VMware ESXi | 7.0, 8.0 all versions | Limited to VMX sandbox |
| VMware Workstation Pro | 17.x versions | Complete host system exposure |
| VMware Fusion | 13.x versions | Complete host system exposure |
| VMware Tools | Windows 11.x, 12.x, 13.x | Memory information disclosure |
While ESXi systems limit exploitation to the VMX sandbox, successful exploitation on Workstation and Fusion can lead to complete host system compromise.
Attack Requirements and Scenarios
Attackers need the following conditions to exploit this vulnerability:
- Local administrative privileges within the virtual machine
- VMCI-enabled environment
- Appropriate exploit code
The typical attack scenario involves an attacker compromising a virtual machine, gaining administrator privileges, and then leveraging the VMCI integer-underflow vulnerability to perform out-of-bounds writes and execute malicious code in the host’s VMX process.
2. Detailed Patch Application Methods for Each VMware Product
VMware ESXi Patching Steps
ESXi 8.0 users must update to ESXi80U3f-24784735 or ESXi80U2e-24789317, while ESXi 7.0 users need ESXi70U3w-24784741.
ESXi 8.0 Update Process:
- vSphere Client Access and Patch Preparation
- Log into vSphere Client with root credentials
- Navigate to Main Menu → Hosts and Clusters
- Patch Application via Update Manager
- Menu → Update Manager
- Under Baselines tab, select Create New Baseline
- Choose Host Patch and search for ESXi80U3f-24784735
- Select patch and add to baseline
- Host Patch Execution
- Select target host → Updates tab
- Click Remediate to begin patch application
- Confirm Maintenance Mode entry
ESXi 7.0 Update Process:
# Command-line patch application via SSH
esxcli software profile update -p ESXi-7.0U3w-24784741-standard -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml
# Perform reboot
reboot
Download Links:
VMware Workstation Pro 17.6.4 Update Procedure
Update VMware Workstation Pro to version 17.6.4 (Build 24832109).
Automatic Update Method:
- Launch VMware Workstation Pro
- Help → Software Updates
- Select Check for Updates Online
- Download and install version 17.6.4 when detected
Manual Download and Installation:
- Access Broadcom Support Portal
- Product Downloads → Search for VMware Workstation Pro
- Select version 17.6.4 for download
- Run installation over existing version
Note: Current automatic update functionality has server issues, making manual download more reliable.
VMware Fusion 13.6.4 macOS Update Guide
Update VMware Fusion to version 13.6.4 (Build 24832108):
- Check Current Version
- Launch VMware Fusion
- VMware Fusion menu → About VMware Fusion
- Execute Update
- VMware Fusion menu → Check for Updates
- Begin automatic download when version 13.6.4 is detected
- Complete Installation and Verification
- Approve installation with administrator privileges
- Restart after installation completion
- Verify version 13.6.4 (Build 24832108) in About information
3. Complete VMware Tools Security Update Guide
VMware Tools should be updated to version 13.0.1.0, which also resolves the CVE-2025-41239 information disclosure vulnerability.
Windows Guest OS Updates
Automatic Update Method:
- Boot Windows in virtual machine
- Start Menu → VMware Tools → Check for VMware Tools Updates
- Download and install when version 13.0.1.0 is detected
Manual Update Method:
- Select VM in vSphere Client
- Actions → Guest OS → Install/Upgrade VMware Tools
- Select Complete Installation
- Run installation wizard within virtual machine
Linux Guest OS Update Procedure
# Check current VMware Tools version
vmware-toolbox-cmd -v
# Update via package manager (Ubuntu/Debian)
sudo apt update
sudo apt install open-vm-tools open-vm-tools-desktop
# RPM-based systems (RHEL/CentOS)
sudo yum update open-vm-tools
4. Post-Patch Security Verification and Confirmation
Patch Verification Through Version Checking
ESXi Version Verification:
# Check version after SSH connection
vmware -vl
# Verify installed VIBs
esxcli software vib list | grep -i vmci
Workstation Pro Version Verification:
- Help → About VMware Workstation Pro
- Confirm build number is 24832109
Fusion Version Verification:
- VMware Fusion menu → About VMware Fusion
- Confirm build number is 24832108
Security Verification Through Vulnerability Scanning
Qualys customers can use QIDs 216348, 216349, 383581, and 383582 to scan for vulnerable assets.
Nessus Scan Configuration:
- Create new scan → Select Advanced Scan
- Plugins tab → Enable VMware-related plugins
- Identify and execute CVE-2025-41237 related plugin IDs
5. Additional Security Hardening Measures and Best Practices
Network Segmentation and Access Control
To further strengthen virtualized environment security, implement these measures:
- Virtual Switch Security Settings: Disable Promiscuous Mode
- Firewall Rule Hardening: Block unnecessary VMCI communication
- Privilege Minimization: Strictly manage administrator privileges within VMs
Continuous Security Monitoring
# ESXi log monitoring
tail -f /var/log/vmware/vmkernel.log | grep -i vmci
# Detect suspicious VMCI activity
grep "VMCI" /var/log/vmware/vmx-*.log
Backup and Recovery Planning
Before applying patches, ensure you perform these backups:
- ESXi host configuration backup
- Critical virtual machine snapshot creation
- vCenter database backup
6. Troubleshooting and Rollback Guide
Response to Patch Application Failures
ESXi Patch Rollback:
# Restore to previous image profile
esxcli software profile update -p [previous_profile_name]
# Revert configuration changes
vim-cmd hostsvc/firmware/restore_defaults
Workstation/Fusion Recovery:
- Control Panel → Programs and Features
- Select VMware product → Change → Repair
Common Installation Error Resolution
Error: “Cannot connect to update server”
- Solution: Proceed with offline installation after manual download
Error: “Insufficient privileges”
- Solution: Retry after running CMD/Terminal as administrator
7. Future Security Management and Recommendations
Regular Security Update Planning
Monitor Broadcom’s VMware security advisories regularly and establish the following management framework:
- Monthly security patch review and application planning
- Pre-verification in test environments before production deployment
- Documentation of patch application history and results
Security Information Subscription and Alert Setup
- Subscribe to VMware Security Blog
- Configure security alerts on Broadcom Support Portal
- Automate CVE database monitoring
Additional technical documentation and frequently asked questions related to CVE-2025-41237 are available in the official FAQ.