CVE-2023-21746 in Windows
Summary
by MITRE • 01/11/2023
Windows NTLM Elevation of Privilege Vulnerability.
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Analysis
by VulDB Data Team • 01/31/2023
This vulnerability represents a critical elevation of privilege flaw within the Windows NTLM authentication protocol that allows attackers to escalate their privileges from a standard user account to SYSTEM level access. The vulnerability stems from improper validation of NTLM authentication tokens during the authentication process, specifically when the system processes forged or manipulated authentication requests. This weakness enables malicious actors to bypass normal authentication controls and gain unauthorized administrative access to target systems. The flaw exists in the core NTLM implementation within Windows operating systems, affecting multiple versions including Windows 10, Windows 11, and various server editions. Attackers can exploit this vulnerability by crafting specially formatted authentication requests that manipulate the NTLM authentication flow, potentially leading to complete system compromise. The vulnerability has been classified under CWE-284 which specifically addresses improper access control mechanisms, and aligns with ATT&CK technique T1078 for valid accounts and T1548 for abuse of privileges. This represents a significant threat to enterprise environments where NTLM authentication is still actively used, particularly in legacy systems or environments with mixed authentication protocols.
The technical exploitation of this vulnerability requires attackers to understand the NTLM authentication handshake process and manipulate specific fields within the authentication tokens to bypass normal validation checks. The flaw manifests when the system fails to properly validate the authentication context and does not adequately verify the legitimacy of the authentication challenge-response sequence. This allows for privilege escalation attacks where an attacker can present forged credentials or manipulate existing authentication states to gain elevated privileges. The vulnerability affects systems that rely on NTLM authentication, including those using legacy applications, domain controllers, and systems with NTLM fallback mechanisms. Attackers typically need to be authenticated to the system or positioned within the network to exploit this vulnerability, making it a medium to high-risk threat in environments where NTLM is still in use. The exploitation process involves careful crafting of authentication messages that can trick the system into accepting unauthorized access requests while maintaining the appearance of legitimate authentication.
Organizations affected by this vulnerability face significant operational risks including complete system compromise, data theft, lateral movement within networks, and potential denial of service conditions. The impact extends beyond individual system compromise to potentially affect entire network infrastructures where NTLM authentication is prevalent. Security teams must consider the widespread nature of NTLM usage in enterprise environments, as many legacy applications and systems continue to rely on this authentication mechanism despite its known security limitations. The vulnerability can enable attackers to establish persistent access, deploy additional malware, or conduct reconnaissance activities without detection. Organizations with insufficient network segmentation or monitoring capabilities face the highest risk of exploitation, as attackers can leverage this vulnerability for extended periods without detection. The presence of this vulnerability also impacts compliance requirements, particularly in regulated environments where strict access controls and privilege management are mandatory.
Mitigation strategies for this vulnerability should focus on immediate remediation through Microsoft security updates and long-term architectural improvements. Organizations must prioritize applying the relevant security patches from Microsoft as soon as they become available, as these updates address the core validation flaws in the NTLM implementation. Network segmentation should be implemented to limit access to systems that rely on NTLM authentication, particularly those with high-value assets. The use of alternative authentication protocols such as Kerberos should be strongly encouraged, as these provide better security properties and are less susceptible to this particular class of vulnerability. Security monitoring should be enhanced to detect unusual authentication patterns or attempts to manipulate authentication tokens. Organizations should conduct comprehensive audits of their authentication infrastructure to identify all systems still relying on NTLM and develop migration plans to more secure alternatives. Additionally, implementing strict access controls, regular privilege reviews, and enhanced logging capabilities will help detect and prevent exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining up-to-date authentication mechanisms and the risks associated with legacy protocols that may contain known security flaws.