CVE-2023-20867 in Tools
Summary
by MITRE • 06/13/2023
A fully compromised ESXi host can force VMware Tools to fail to authenticate host-to-guest operations, impacting the confidentiality and integrity of the guest virtual machine.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability identified as CVE-2023-20867 represents a critical security flaw within VMware's ESXi hypervisor platform that specifically targets the authentication mechanisms between host and guest virtual machines. This vulnerability exists within the VMware Tools component, which serves as a critical communication bridge facilitating various management and operational functions between the hypervisor and its virtualized guests. The flaw allows an attacker who has already achieved full compromise of an ESXi host to manipulate the authentication process, effectively undermining the security controls that protect guest virtual machine data and operations.
The technical implementation of this vulnerability stems from improper handling of authentication tokens and session management within the VMware Tools service running on compromised hosts. When an attacker gains complete control over an ESXi host, they can exploit this weakness to inject malicious authentication requests or manipulate existing authentication flows, causing VMware Tools to reject legitimate host-to-guest communications while potentially allowing unauthorized access to guest systems. This authentication failure creates a scenario where the integrity and confidentiality of guest virtual machine data can be compromised, as the system may permit unauthorized operations or fail to properly validate legitimate administrative actions.
The operational impact of CVE-2023-20867 extends beyond simple authentication failures, as it fundamentally undermines the security isolation that virtualization platforms are designed to provide. Attackers can leverage this vulnerability to bypass critical security controls that separate guest operating systems from each other and from the underlying host infrastructure. This weakness particularly affects environments where multiple tenants share the same hypervisor infrastructure, as it could enable cross-tenant data leakage or unauthorized access to sensitive guest systems. The vulnerability's exploitation requires prior compromise of the ESXi host, making it a post-compromise attack vector that can be used to escalate privileges and maintain persistence within virtualized environments.
Organizations should implement immediate mitigations including applying VMware's official security patches and updates, which address the authentication flow issues within VMware Tools. Network segmentation and monitoring should be enhanced to detect anomalous authentication patterns or unusual VMware Tools behavior. Security teams must also review and strengthen their host-based intrusion detection systems to identify potential exploitation attempts. The vulnerability aligns with CWE-287, which addresses improper authentication issues, and maps to ATT&CK techniques related to privilege escalation and credential access. Additionally, organizations should consider implementing micro-segmentation strategies and enhanced logging of VMware Tools activities to detect potential exploitation attempts and maintain visibility into host-to-guest communication flows.