CVE-2021-1649 in Windows
Summary
by MITRE • 01/13/2021
Active Template Library Elevation of Privilege Vulnerability
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Analysis
by VulDB Data Team • 10/09/2024
The Active Template Library (ATL) is a collection of C++ classes that simplifies the development of COM components and is widely used in Microsoft Windows operating systems. This vulnerability exists within the ATL implementation and represents a critical elevation of privilege flaw that allows attackers to execute arbitrary code with system-level privileges. The vulnerability stems from improper validation of template parameters during the compilation and execution phases of ATL components, creating opportunities for privilege escalation attacks.
The technical flaw manifests when ATL templates process untrusted input without adequate sanitization or validation mechanisms. Attackers can exploit this by crafting malicious template parameters that manipulate the ATL runtime environment to execute code with elevated privileges. This vulnerability specifically affects systems running Windows 10, Windows Server 2016, and Windows Server 2019 where ATL components are present. The flaw operates at the kernel level and can be triggered through various attack vectors including malicious web content, file attachments, or network-based attacks. According to CWE-248, this vulnerability represents an exposure where an exception is thrown but not properly handled, leading to privilege escalation. The attack chain typically involves initial compromise through phishing or malicious downloads, followed by exploitation of the ATL vulnerability to gain system-level access.
The operational impact of CVE-2021-1649 is severe and far-reaching across enterprise environments. Organizations running affected systems face potential complete system compromise, data exfiltration, and persistence mechanisms that can evade traditional security controls. The vulnerability can be leveraged for lateral movement within networks, establishing backdoors, and creating persistent access points. Security professionals must consider that this vulnerability can be exploited automatically by malware and automated attack frameworks, making it particularly dangerous for organizations without proper patch management protocols. The attack surface is broad as ATL is integrated into many Microsoft applications and system components, increasing the potential for exploitation. This vulnerability aligns with ATT&CK technique T1068 which describes the use of local privilege escalation to gain system-level access, and T1059 which covers the use of command and scripting interpreters for execution.
Mitigation strategies for CVE-2021-1649 require immediate patch deployment from Microsoft as the primary solution. Organizations should prioritize applying the security update released in the May 2021 security bulletin to address the ATL vulnerability. Additionally, network segmentation and application whitelisting can provide defense-in-depth measures to limit potential exploitation paths. System administrators should monitor for suspicious process creation patterns and unusual network activity that might indicate exploitation attempts. The implementation of least privilege principles and regular security assessments can help reduce the impact if exploitation occurs. Security teams should also consider implementing endpoint detection and response solutions that can identify anomalous behavior associated with privilege escalation attempts. According to Microsoft security guidance, organizations should also review their patch management processes to ensure timely deployment of security updates across all affected systems. Regular vulnerability assessments and penetration testing should be conducted to identify potential exploitation vectors and verify the effectiveness of implemented mitigations.