CVE-2020-3960 in ESXi
Summary
by MITRE • 09/15/2021
VMware ESXi (6.7 before ESXi670-202006401-SG and 6.5 before ESXi650-202005401-SG), Workstation (15.x before 15.5.5), and Fusion (11.x before 11.5.5) contain an out-of-bounds read vulnerability in NVMe functionality. A malicious actor with local non-administrative access to a virtual machine with a virtual NVMe controller present may be able to read privileged information contained in physical memory.
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Analysis
by VulDB Data Team • 09/17/2021
The vulnerability identified as CVE-2020-3960 represents a critical out-of-bounds read flaw within VMware's virtualization platforms affecting ESXi, Workstation, and Fusion products. This security weakness resides in the NVMe (Non-Volatile Memory Express) functionality implementation, specifically when virtual machines are configured with virtual NVMe controllers. The flaw stems from insufficient bounds checking during NVMe command processing, creating a scenario where malicious code can exploit memory access patterns to retrieve sensitive data from physical memory locations. The vulnerability is particularly concerning because it requires only local access within a compromised virtual machine, making it accessible to attackers who have already achieved initial compromise through other means.
The technical exploitation of this vulnerability occurs when a malicious actor executes code within a guest operating system that has access to a virtual NVMe controller. The out-of-bounds read allows the attacker to access memory regions that should remain protected from guest-level access, potentially exposing kernel memory contents, cryptographic keys, or other privileged information. This type of vulnerability maps directly to CWE-125, which describes out-of-bounds read conditions, and represents a classic example of insufficient input validation in virtualized environments. The attack vector is classified as local privilege escalation within the virtual machine context, but the impact extends beyond the guest to potentially compromise the underlying host system's memory space.
The operational impact of CVE-2020-3960 is significant for organizations utilizing VMware virtualization solutions, particularly those with multiple virtual machines running on shared hosts. Attackers who successfully exploit this vulnerability can potentially extract sensitive information that could be used for further attacks, including credential theft, privilege escalation, or information disclosure attacks. The vulnerability affects a wide range of VMware products including ESXi versions 6.7 and 6.5, Workstation 15.x, and Fusion 11.x, making it a widespread concern across enterprise virtualization environments. This weakness creates a potential pathway for attackers to bypass traditional security boundaries between virtual machines and the host system, undermining the fundamental isolation principles that virtualization platforms are designed to maintain.
Organizations should immediately apply the vendor-provided patches to all affected VMware products, with particular attention to ESXi hosts running vulnerable versions. The recommended mitigation strategy involves updating to the latest patch releases for ESXi 6.7 and 6.5, as well as upgrading VMware Workstation 15.x to version 15.5.5 and Fusion 11.x to version 11.5.5. Network segmentation and access controls should be enhanced to limit the potential impact of local compromise within virtual machines. Additionally, organizations should implement monitoring for unusual memory access patterns and consider reducing the number of virtual NVMe controllers in use where possible. The vulnerability's classification under the ATT&CK framework includes techniques related to privilege escalation and credential access, making it a critical target for defensive measures in zero-trust security models. Regular vulnerability assessments should include verification of NVMe controller configurations and monitoring for unauthorized access attempts to virtual hardware components.