CVE-2021-42285 in Windows
Summary
by MITRE • 11/10/2021
Windows Kernel Elevation of Privilege Vulnerability
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Analysis
by VulDB Data Team • 11/12/2021
The vulnerability identified as CVE-2021-42285 represents a critical Windows kernel elevation of privilege vulnerability that affects multiple Windows operating systems including Windows 10, Windows Server 2016, and Windows Server 2019. This flaw resides within the Windows kernel component and specifically impacts how the operating system handles certain privilege escalation scenarios. The vulnerability stems from improper validation of kernel-mode operations that allows malicious code to potentially elevate privileges from a standard user account to SYSTEM level access, effectively compromising the entire system. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-264, which describes permissions, privileges, and access controls issues within operating systems. The flaw demonstrates the classic characteristics of a kernel-level privilege escalation vulnerability where insufficient input validation and access control mechanisms enable unauthorized privilege elevation.
The technical exploitation of CVE-2021-42285 occurs through manipulation of kernel-mode operations that should normally be restricted to privileged processes only. Attackers can leverage this vulnerability by crafting specific payloads that exploit the improper handling of kernel objects and memory management operations. The vulnerability specifically affects the Windows kernel's privilege checking mechanisms, particularly in how it validates access to kernel resources and handles privilege transitions. This flaw allows an attacker with low-privilege access to potentially execute malicious code with elevated privileges, effectively bypassing the normal Windows security model. The vulnerability is particularly dangerous because it operates at the kernel level where the operating system's core security controls are implemented, making it extremely difficult to detect and prevent through traditional endpoint protection mechanisms.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as successful exploitation can result in complete system compromise and persistent access to network resources. Organizations running affected Windows versions face significant risk of data breaches, lateral movement attacks, and persistent threat actor presence within their networks. The vulnerability can be exploited remotely or locally, depending on the specific attack vector and system configuration, making it particularly dangerous in enterprise environments where multiple users have varying levels of system access. Security researchers have noted that this vulnerability can be combined with other exploits to create more sophisticated attack chains, potentially leading to full domain compromise in Active Directory environments. The impact is further amplified by the fact that Windows kernel vulnerabilities typically have broad scope across multiple Windows versions and configurations.
Mitigation strategies for CVE-2021-42285 primarily focus on immediate patch deployment through Microsoft's regular security updates, which address the underlying kernel privilege validation flaws. Organizations should prioritize patching all affected Windows systems, particularly those running Windows 10 versions 1607, 1803, 1809, 1903, 1909, and 2004, as well as Windows Server 2016 and 2019 versions. Network segmentation and access control measures should be implemented to limit potential attack surfaces, while monitoring systems should be enhanced to detect anomalous privilege escalation activities. The vulnerability aligns with ATT&CK technique T1068, which describes local privilege escalation through kernel exploits, making it a high-priority target for threat hunting and incident response teams. Additional defensive measures include implementing application whitelisting policies, disabling unnecessary services, and maintaining up-to-date security information and event management systems to detect exploitation attempts. Organizations should also consider implementing just-in-time compilation controls and kernel-mode driver verification to prevent exploitation of similar kernel-level vulnerabilities.