CriticalFebruary 10, 2026
Mass VMware ESXi Ransomware Campaign Targeting Virtual Infrastructure
Large-scale ransomware campaign exploiting VMware ESXi vulnerabilities to encrypt virtual machines and disrupt business operations. Attackers leverage CVE-2021-21974 to compromise unpatched systems globally.
Information TechnologyFinancial ServicesHealthcareManufacturingGovernmentTelecommunications
A significant ransomware campaign dubbed 'ESXiArgs' is actively targeting VMware ESXi hypervisors worldwide, primarily exploiting CVE-2021-21974, a two-year-old heap overflow vulnerability in the OpenSLP service. The attack has impacted thousands of servers across multiple countries, with particularly high concentrations in France, Germany, and North America.
The ransomware specifically targets ESXi virtual machines, encrypting VM files (including .vmdk, .vmx, .vmxf, and .nvram) and effectively disrupting organizations' virtualized infrastructure. The campaign demonstrates sophisticated targeting of enterprise virtualization platforms, potentially causing widespread business disruption due to the critical nature of affected systems.
Key Findings
- A significant ransomware campaign dubbed 'ESXiArgs' is actively targeting VMware ESXi hypervisors worldwide, primarily exploiting CVE-2021-21974, a two-year-old heap overflow vulnerability in the OpenSLP service
- The attack has impacted thousands of servers across multiple countries, with particularly high concentrations in France, Germany, and North America
- The ransomware specifically targets ESXi virtual machines, encrypting VM files (including
- nvram) and effectively disrupting organizations' virtualized infrastructure
Overview
A widespread ransomware campaign is actively targeting VMware ESXi hypervisors, exploiting known vulnerabilities to encrypt virtual machines and associated files. The attack, identified as 'ESXiArgs,' has affected thousands of servers globally, with significant impact on critical business operations.
Attack Vector
The primary attack vector is CVE-2021-21974, a heap overflow vulnerability in the OpenSLP service of ESXi that allows for remote code execution. This vulnerability affects ESXi versions 6.5, 6.7, and 7.0.
Technical Analysis
The ransomware specifically targets files essential to virtual machine operations:
- .vmdk (Virtual Machine Disk) files
- .vmx (Virtual Machine Configuration) files
- .vmxf (Virtual Machine Extended Configuration) files
- .nvram (Virtual Machine BIOS) files
The encryption process utilizes a combination of symmetric and asymmetric encryption, making recovery without the decryption key extremely difficult. The ransomware also attempts to stop virtual machines before encryption and removes VM snapshots to prevent easy recovery.
Impact Assessment
- Complete encryption of virtual infrastructure
- Business continuity disruption
- Potential data loss
- Significant recovery time and costs
Recommendations
Immediate actions required:
- Patch all ESXi hosts to the latest version
- Disable the OpenSLP service if not required
- Implement network segmentation for ESXi management interfaces
- Ensure robust backup solutions are in place and tested
- Monitor ESXi logs for suspicious activities
- Implement strong access controls and MFA for management interfaces
Indicators of Compromise
- Presence of .args files in /tmp directory
- Encrypted files with .vmxf extension
- Suspicious connections to TCP port 427 (SLP)
- Unusual ESXi process activity