CVE-2021-41342 in Windows
Summary
by MITRE • 10/13/2021
Windows MSHTML Platform Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 10/15/2021
The CVE-2021-41342 vulnerability represents a critical remote code execution flaw within the Windows MSHTML platform that affects multiple Windows operating systems including Windows 10, Windows Server 2016, and Windows Server 2019. This vulnerability resides in the HTML parsing and rendering engine that processes web content and local HTML files within the Windows environment. The flaw specifically impacts how the MSHTML component handles certain malformed or crafted HTML content, creating opportunities for attackers to execute arbitrary code on targeted systems. The vulnerability is particularly concerning because it can be exploited through various attack vectors including malicious websites, email attachments, and compromised web applications that render HTML content. Security researchers have identified this as a remote code execution vulnerability that could allow an attacker with minimal privileges to gain full system control without requiring user interaction in many scenarios, making it a significant threat to enterprise environments and individual users alike.
The technical nature of CVE-2021-41342 stems from improper input validation and memory handling within the MSHTML component of Windows. When processing specific HTML elements or attributes, the platform fails to properly validate memory boundaries, leading to potential buffer overflow conditions or memory corruption scenarios. This flaw typically manifests when the HTML parser encounters malformed content that triggers unexpected behavior in the rendering engine's memory management subsystem. The vulnerability is categorized under CWE-121, which describes stack-based buffer overflow conditions, and may also relate to CWE-787, representing out-of-bounds write operations. The root cause involves the MSHTML engine's insufficient bounds checking when processing complex HTML structures, particularly those involving nested elements, scripting references, or dynamic content manipulation. Attackers can leverage this weakness by crafting malicious HTML content that, when processed by the vulnerable Windows component, triggers memory corruption and subsequently allows for code execution.
The operational impact of this vulnerability extends across multiple threat vectors and attack scenarios within enterprise and consumer environments. Organizations running affected Windows versions face potential compromise through drive-by downloads, compromised websites, and spear-phishing campaigns that deliver malicious HTML content. The vulnerability's exploitation capability means that attackers can bypass traditional security controls including firewalls and antivirus solutions, as the code execution occurs within the legitimate Windows platform components. The risk is particularly elevated in environments where users frequently browse the internet or interact with untrusted web content. According to ATT&CK framework categorization, this vulnerability aligns with T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, as successful exploitation can lead to system-level privileges. The vulnerability affects both domain-joined and standalone systems, making it a universal threat that requires immediate attention from security administrators. Additionally, the remote nature of the exploit means that attackers can operate from anywhere in the world without requiring physical access to target systems, significantly expanding the attack surface.
Mitigation strategies for CVE-2021-41342 should include immediate deployment of Microsoft security patches and updates, which address the underlying memory handling flaws in the MSHTML component. Organizations should implement network segmentation and web filtering controls to reduce exposure to potentially malicious content, while also deploying enhanced endpoint detection and response solutions that can identify anomalous behavior associated with exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify systems running affected Windows versions and prioritize patching efforts accordingly. The implementation of application whitelisting policies can help prevent execution of unauthorized HTML content, while regular security monitoring should be established to detect potential exploitation attempts. Additional protective measures include disabling unnecessary web browsing features, implementing strict email filtering rules, and maintaining updated threat intelligence feeds that can identify known malicious domains and content associated with this vulnerability. Regular security awareness training for users can also reduce the risk of successful social engineering attacks that leverage this vulnerability, as users need to understand the dangers of visiting untrusted websites or opening suspicious email attachments that could trigger the exploit conditions.