CVE-2021-42287 in Windows
Summary
by MITRE • 11/10/2021
Active Directory Domain Services Elevation of Privilege Vulnerability
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Analysis
by VulDB Data Team • 10/30/2025
This vulnerability resides within Active Directory Domain Services and represents a critical elevation of privilege flaw that allows attackers to escalate their privileges from standard user level to domain administrator level. The vulnerability stems from improper validation of the machine account name during the authentication process, specifically when a machine account is created or updated. This flaw enables malicious actors to manipulate the authentication flow by crafting specially crafted machine account names that bypass normal security controls. The technical implementation involves the absence of proper validation checks that should occur when processing machine account creation requests, allowing an attacker to submit a machine account name that contains a domain administrator account name, thereby gaining unauthorized access to domain-level privileges. The vulnerability impacts all versions of Windows Server that support Active Directory Domain Services, particularly those running Windows Server 2016, 2019, and 2022, though older versions may also be affected depending on their configuration and patch status. This weakness aligns with CWE-287 which addresses improper authentication and is closely related to ATT&CK technique T1078 which covers valid accounts and privilege escalation through legitimate credentials. The operational impact is severe as it allows attackers to establish persistent access to domain environments, potentially enabling them to move laterally throughout the network, access sensitive data, and compromise the entire domain infrastructure. Attackers can leverage this vulnerability to create domain administrator accounts without requiring legitimate administrative credentials, effectively bypassing the normal authentication and authorization mechanisms that protect domain resources. The attack vector typically involves an attacker first gaining access to a domain-joined machine or obtaining a user account with minimal privileges, then using the vulnerability to escalate their access rights. This vulnerability is particularly dangerous because it can be exploited without requiring elevated privileges initially, making it a prime target for attackers seeking to establish persistent access to enterprise environments. The exploitation process requires careful crafting of machine account names that contain the target administrator account name, allowing the attacker to impersonate that account during authentication. Organizations should implement immediate mitigations including disabling the ability to create machine accounts with names that match domain administrator accounts, applying the relevant Microsoft security patches, and monitoring for unusual machine account creation activities. Additionally, network segmentation and the principle of least privilege should be enforced to limit the potential damage from successful exploitation. The vulnerability also highlights the importance of proper input validation and account name sanitization in authentication systems, as it demonstrates how insufficient validation can lead to complete privilege escalation. Security teams should also consider implementing additional monitoring for machine account creation events and conducting regular audits of domain accounts to detect potential exploitation attempts. This vulnerability underscores the critical importance of maintaining up-to-date security patches and the need for robust authentication mechanisms within enterprise environments. The flaw represents a fundamental weakness in the domain authentication process that can be exploited to gain complete control over domain resources. Organizations must ensure that all domain controllers are properly patched and that appropriate security controls are in place to prevent unauthorized account creation and privilege escalation attempts. The vulnerability also emphasizes the need for continuous monitoring and threat detection capabilities that can identify anomalous authentication patterns and unauthorized account manipulations within Active Directory environments. Proper configuration management and regular security assessments are essential to prevent exploitation of this type of vulnerability and maintain the integrity of domain authentication systems.