CVE-2020-4005 in ESXi
Summary
by MITRE • 11/21/2020
VMware ESXi (7.0 before ESXi70U1b-17168206, 6.7 before ESXi670-202011101-SG, 6.5 before ESXi650-202011301-SG) contains a privilege-escalation vulnerability that exists in the way certain system calls are being managed. A malicious actor with privileges within the VMX process only, may escalate their privileges on the affected system. Successful exploitation of this issue is only possible when chained with another vulnerability (e.g. CVE-2020-4004)
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2020-4005 represents a critical privilege escalation flaw within VMware ESXi hypervisor implementations across multiple versions including 7.0 before ESXi70U1b-17168206, 6.7 before ESXi670-202011101-SG, and 6.5 before ESXi650-202011301-SG. This vulnerability specifically targets the management of certain system calls within the hypervisor's virtual machine execution environment, creating a pathway for malicious actors to elevate their privileges beyond the intended boundaries of the VMX process. The flaw exists in the underlying privilege management mechanisms that control how system calls are processed and validated within the ESXi hypervisor architecture.
The technical implementation of this vulnerability stems from improper validation and handling of system calls that are executed within the context of the VMX process, which is responsible for managing virtual machine execution environments. When a malicious actor gains access to execute code within the VMX process, they can exploit this flaw to manipulate the privilege escalation mechanisms that should normally prevent unauthorized elevation of privileges. The vulnerability's exploitation requires a specific sequence of operations that leverages the inherent trust model of the hypervisor's privilege management system, where system calls that should be restricted are improperly validated. This weakness allows for the creation of elevated privilege contexts that bypass normal access controls and security boundaries established by the hypervisor's privilege separation mechanisms.
The operational impact of CVE-2020-4005 is significant as it provides attackers with a mechanism to gain unauthorized administrative access to ESXi hosts, potentially leading to complete compromise of the virtualized environment. When successfully exploited, this vulnerability enables attackers to perform actions such as creating new administrative accounts, modifying system configurations, accessing sensitive data stored in virtual machines, and potentially escalating to root-level privileges on the underlying physical host. The vulnerability's chaining requirement with other exploits like CVE-2020-4004 demonstrates how attackers may combine multiple weaknesses to overcome the security boundaries of the hypervisor. This chaining capability makes the vulnerability particularly dangerous in environments where multiple vulnerabilities exist and can be leveraged in coordinated attacks. The impact extends beyond individual virtual machines to potentially compromise entire virtualized infrastructures, as the attacker can gain access to the hypervisor's management plane and control all virtual machines running on the compromised host.
Security mitigations for CVE-2020-4005 primarily involve applying the vendor-provided patches and updates that address the privilege escalation mechanisms within the ESXi hypervisor. VMware released specific updates for each affected version, including ESXi70U1b-17168206, ESXi670-202011101-SG, and ESXi650-202011301-SG, which correct the improper system call validation and privilege management flaws. Organizations should implement comprehensive patch management procedures to ensure timely deployment of these security updates across all ESXi hosts in their environment. Additional mitigations include implementing network segmentation to limit access to ESXi management interfaces, restricting physical access to hypervisor hosts, and monitoring for suspicious privilege escalation activities. The vulnerability aligns with CWE-276, which describes improper privilege management, and maps to ATT&CK technique T1068, which involves exploiting weaknesses in privilege escalation mechanisms. Organizations should also consider implementing zero-trust network principles and regular security assessments to identify potential exploitation vectors that could lead to similar privilege escalation scenarios.