CVE-2021-22045 Overview
CVE-2021-22045 is a heap-overflow vulnerability affecting the CD-ROM device emulation component in VMware ESXi, VMware Workstation, and VMware Fusion virtualization products. A malicious actor with access to a virtual machine that has CD-ROM device emulation enabled may be able to exploit this vulnerability in conjunction with other issues to achieve code execution on the hypervisor from within a virtual machine, enabling a virtual machine escape attack.
Critical Impact
Successful exploitation could allow an attacker to escape from a guest virtual machine and execute arbitrary code on the host hypervisor, potentially compromising the entire virtualization infrastructure and all hosted virtual machines.
Affected Products
- VMware ESXi 7.0 (all versions)
- VMware ESXi 6.7 (versions before ESXi670-202111101-SG)
- VMware ESXi 6.5 (versions before ESXi650-202110101-SG)
- VMware Workstation 16.2.0
- VMware Fusion 12.2.0
- VMware Cloud Foundation (versions 3.x and 4.x)
Discovery Timeline
- 2022-01-04 - CVE-2021-22045 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2021-22045
Vulnerability Analysis
This vulnerability exists in the CD-ROM device emulation subsystem of VMware's virtualization products. The heap-overflow condition occurs when processing certain CD-ROM device operations within a guest virtual machine. The vulnerability is particularly significant because it affects the hypervisor's device emulation layer, which runs with elevated privileges on the host system.
The attack requires local access to a virtual machine and low privileges within the guest operating system. While the attack complexity is considered high due to the need to chain this vulnerability with other issues for successful exploitation, the potential impact is severe. Successful exploitation could result in complete compromise of confidentiality, integrity, and availability of the host system and all co-located virtual machines.
VM escape vulnerabilities like this one are highly prized in virtualized environments because they break the fundamental security boundary between guest and host systems, potentially exposing multiple tenants in cloud or enterprise virtualization deployments.
Root Cause
The root cause is an out-of-bounds write vulnerability (CWE-787) in the CD-ROM device emulation code. The heap-overflow occurs due to improper bounds checking when handling specific CD-ROM device requests, allowing memory corruption in the hypervisor's address space. This type of memory corruption vulnerability can be leveraged to overwrite critical data structures and redirect code execution.
Attack Vector
The attack vector requires local access to a guest virtual machine with CD-ROM device emulation enabled. An attacker must:
- Gain access to a virtual machine running on a vulnerable hypervisor
- Ensure the VM has a virtual CD-ROM device configured
- Craft malicious CD-ROM device requests that trigger the heap-overflow condition
- Chain this vulnerability with additional techniques to achieve reliable code execution on the hypervisor
The local attack vector and high complexity requirements reduce the immediate risk, but the potential for VM escape makes this a significant concern for virtualized infrastructure.
Detection Methods for CVE-2021-22045
Indicators of Compromise
- Unexpected crashes or instability in VMware hypervisor services related to CD-ROM device handling
- Unusual memory access patterns or heap corruption signatures in VMware process memory
- Anomalous CD-ROM device activity from guest virtual machines that don't have legitimate CD-ROM access requirements
- Evidence of post-exploitation activity on ESXi hosts originating from guest VM contexts
Detection Strategies
- Monitor VMware ESXi host logs for abnormal CDROM device operations or unexpected service crashes
- Implement behavioral analysis on hypervisor systems to detect unusual device emulation activity
- Deploy endpoint detection and response (EDR) solutions capable of monitoring virtualization layer activity
- Review vCenter and ESXi audit logs for signs of unauthorized access or configuration changes
Monitoring Recommendations
- Enable verbose logging for VMware services and forward logs to a centralized SIEM for correlation
- Monitor for unusual patterns of VM-to-host communication that could indicate exploitation attempts
- Implement network segmentation to limit lateral movement if a VM escape occurs
- Regularly audit which VMs have CD-ROM devices attached and remove unnecessary virtual hardware
How to Mitigate CVE-2021-22045
Immediate Actions Required
- Apply the appropriate security patches from VMware immediately for all affected products
- Remove or disconnect virtual CD-ROM devices from VMs where they are not required
- Review and restrict which users and processes have access to virtual machine configurations
- Implement additional monitoring on hypervisor hosts to detect potential exploitation attempts
Patch Information
VMware has released security patches addressing this vulnerability. Organizations should apply the following updates:
- ESXi 6.5: Update to ESXi650-202110101-SG or later
- ESXi 6.7: Update to ESXi670-202111101-SG or later
- ESXi 7.0: Apply the latest security patches from VMware
- Workstation: Update to a patched version beyond 16.2.0
- Fusion: Update to a patched version beyond 12.2.0
- Cloud Foundation: Apply the relevant VMware Cloud Foundation updates
Refer to VMware Security Advisory VMSA-2022-0001 for complete patch details and download links.
Workarounds
- Remove CD-ROM devices from virtual machine configurations where they are not operationally required using vSphere Client or esxcli
- Disable virtual CD-ROM device access at the VM policy level to reduce the attack surface
- Implement strict access controls to limit which administrators can modify VM hardware configurations
- Consider using ISO images mounted via datastore rather than emulated CD-ROM devices where possible
# Remove CD-ROM device from a VM using esxcli (example)
# First, power off the VM and note the VM ID
# List VMs to get the VM ID
vim-cmd vmsvc/getallvms
# Check current VM hardware configuration
vim-cmd vmsvc/device.getdevices <vmid>
# Edit the VMX file to remove CD-ROM device entries
# Backup the VMX file first, then remove cdrom device lines
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
