CVE-2020-1567 in Internet Explorer
Summary
by MITRE
A remote code execution vulnerability exists in the way that the MSHTML engine improperly validates input. An attacker could execute arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker who successfully exploited the vulnerability could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. In a HTML editing attack scenario, an attacker could trick a user into editing a specially crafted file that is designed to exploit the vulnerability. The security update addresses the vulnerability by modifying how MSHTML engine validates input.
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability identified as CVE-2020-1567 represents a critical remote code execution flaw within Microsoft's MSHTML engine, which serves as the core rendering component for Internet Explorer and other Microsoft applications. This vulnerability stems from improper input validation mechanisms within the engine's processing logic, creating a pathway for malicious actors to execute arbitrary code on affected systems. The MSHTML engine's failure to adequately sanitize user-supplied data during HTML parsing operations allows attackers to craft malicious input that bypasses normal security boundaries. This flaw specifically impacts systems where Internet Explorer is installed or where applications rely on the MSHTML rendering engine for processing web content, making it particularly dangerous in enterprise environments where legacy applications continue to utilize this technology. The vulnerability's classification aligns with CWE-129, which addresses issues related to insufficient input validation, and represents a direct violation of secure coding principles that require comprehensive sanitization of all external inputs.
The technical exploitation of CVE-2020-1567 occurs when the MSHTML engine processes malformed HTML content that contains specially crafted input sequences designed to trigger the validation bypass. Attackers can leverage this vulnerability through various attack vectors including malicious websites, email attachments, or specially crafted documents that when opened by vulnerable applications. The exploitation process typically involves constructing HTML content that exploits the engine's parsing logic to execute malicious code within the context of the current user session. When successful, the vulnerability allows attackers to execute code with the privileges of the current user, which can escalate to system-level control if the user has administrative rights. This privilege escalation capability makes the vulnerability particularly dangerous as it can enable complete system compromise without requiring additional exploitation steps. The ATT&CK framework categorizes this vulnerability under T1203 - Exploitation for Client Execution, as it leverages client-side application vulnerabilities to achieve remote code execution.
The operational impact of CVE-2020-1567 extends beyond simple code execution, as it can result in complete system compromise and persistent access for threat actors. Successful exploitation enables attackers to install malicious software, modify or delete critical system data, and create new user accounts with full administrative privileges. This comprehensive control over affected systems can lead to data breaches, system downtime, and broader network infiltration. The vulnerability's remote nature means that attackers can exploit it without requiring physical access to target systems, making it particularly dangerous in environments where users frequently interact with untrusted web content. Organizations running legacy systems or applications that depend on MSHTML engine functionality face significant risk, as the vulnerability can persist even when other security controls are in place. The attack scenario described in the vulnerability description indicates that users can be tricked into editing specially crafted files, which represents a common social engineering approach that can bypass traditional security measures.
Microsoft's security update for CVE-2020-1567 addresses the vulnerability by modifying the MSHTML engine's input validation procedures to properly sanitize and validate all user-supplied content before processing. The fix involves strengthening the engine's parsing logic to reject potentially malicious input sequences and implement more robust validation checks during HTML content processing. Organizations should prioritize applying this security update across all affected systems, particularly those running Internet Explorer or applications that utilize the MSHTML engine. The mitigation strategy should include comprehensive testing of the update in controlled environments to ensure compatibility with existing applications and workflows. Additionally, organizations should consider implementing additional security controls such as browser isolation, web application firewalls, and user education programs to reduce the attack surface. Security teams should monitor for exploitation attempts and implement network-based detection measures to identify potential attacks targeting this vulnerability. The update represents a crucial defensive measure that aligns with industry best practices for addressing client-side vulnerabilities and demonstrates the importance of maintaining up-to-date security patches in protecting enterprise environments from known exploitation techniques.