CVE-2021-1647 in Defender
Summary
by MITRE • 01/13/2021
Microsoft Defender Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 10/09/2024
Microsoft Defender remote code execution vulnerability CVE-2021-1647 represents a critical security flaw in the Windows Defender antivirus solution that could allow attackers to execute arbitrary code on affected systems. This vulnerability specifically affects Microsoft Defender's handling of certain file types during the scanning process, creating a potential attack vector for privilege escalation and system compromise. The flaw exists in the way Defender processes and analyzes specific file formats, particularly those that contain malformed or specially crafted data structures that trigger unexpected behavior in the antivirus engine.
The technical implementation of this vulnerability stems from insufficient input validation and memory handling within Microsoft Defender's file analysis modules. When the antivirus engine encounters certain maliciously crafted files, it fails to properly sanitize the input data before processing, leading to memory corruption that can be exploited by attackers. This type of vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow conditions. The vulnerability is particularly dangerous because it operates at the system level where Defender runs with elevated privileges, potentially allowing attackers to bypass standard user access controls and execute malicious code with system-level permissions.
From an operational perspective, this vulnerability poses significant risk to enterprise environments where Microsoft Defender is actively deployed as the primary antivirus solution. Attackers could leverage this flaw to gain unauthorized access to systems without requiring user interaction or specific exploitation prerequisites, making it particularly dangerous for organizations that rely heavily on Windows Defender for security protection. The attack surface expands when considering that Defender runs continuously in the background and processes numerous file types, creating multiple potential entry points for exploitation. According to ATT&CK framework, this vulnerability maps to T1059.001 for command and script interpreter and T1068 for exploit for privilege escalation, as attackers could use the vulnerability to execute commands with elevated privileges.
The impact of exploitation could result in complete system compromise, data theft, lateral movement within networks, and potential establishment of persistent backdoors. Organizations with vulnerable versions of Windows Defender would be at risk of advanced persistent threats that could remain undetected for extended periods. The vulnerability's severity is compounded by the fact that many organizations may not immediately patch their systems, especially in enterprise environments where patch management processes are complex and time-consuming. Microsoft addressed this vulnerability through security updates that improved input validation and memory handling within Defender's file processing components, requiring administrators to apply the latest security patches to mitigate the risk.
Effective mitigation strategies include immediate deployment of Microsoft's security updates, implementation of network segmentation to limit lateral movement, and enhanced monitoring of system processes for suspicious activity. Security teams should also consider implementing additional layers of protection such as application whitelisting, intrusion detection systems, and regular vulnerability assessments. Organizations should review their patch management processes to ensure timely deployment of security updates across all systems. The vulnerability demonstrates the critical importance of maintaining up-to-date security solutions and highlights the need for comprehensive security testing of antivirus and security software to identify potential flaws before they can be exploited by malicious actors.