CVE-2020-0686 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists in the Windows Installer when MSI packages process symbolic links, aka 'Windows Installer Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2020-0683.
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Analysis
by VulDB Data Team • 03/29/2024
The vulnerability identified as CVE-2020-0686 represents a critical elevation of privilege flaw within the Windows Installer component that specifically manifests when processing symbolic links in MSI packages. This issue resides in the Windows Installer service which handles the installation and configuration of software packages on Microsoft Windows operating systems. The vulnerability stems from improper handling of symbolic link resolution during the installation process, creating a pathway for malicious actors to escalate their privileges from standard user level to system level access. The flaw is particularly concerning because it leverages the legitimate Windows Installer functionality to execute unauthorized code with elevated privileges, making it a sophisticated attack vector that bypasses normal security boundaries.
The technical exploitation of this vulnerability occurs when a malicious MSI package contains symbolic links that point to protected system locations or files. During the installation process, the Windows Installer service follows these symbolic links without proper validation of the target paths, allowing an attacker to redirect installation operations to write files in system directories or execute arbitrary code with elevated privileges. This behavior directly violates the principle of least privilege and creates a persistent backdoor mechanism within the Windows operating system. The vulnerability is classified under CWE-264, which specifically addresses permissions, privileges, and access controls, as it enables unauthorized privilege escalation through improper access control mechanisms. The flaw demonstrates a fundamental weakness in the installer's symbolic link resolution logic, where the system fails to properly validate or sanitize the targets of symbolic links before executing installation operations.
The operational impact of CVE-2020-0686 extends beyond simple privilege escalation, as it provides attackers with the capability to install malicious software, modify system configurations, and potentially establish persistent access to affected systems. When exploited successfully, this vulnerability allows attackers to gain system-level access without requiring administrator credentials, effectively bypassing the security model that separates user applications from system-level operations. The vulnerability affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, making it a widespread concern across enterprise environments. Attackers can leverage this vulnerability through various attack vectors including phishing emails containing malicious MSI attachments, drive-by downloads from compromised websites, or supply chain attacks where legitimate software packages are tampered with to include malicious symbolic links. The implications for enterprise security are severe as this vulnerability can be exploited silently in the background, allowing attackers to establish persistent footholds within networks without detection.
Organizations should implement multiple layers of defense to mitigate the risks associated with CVE-2020-0686. The primary mitigation involves applying the Microsoft security update released in June 2020, which addresses the symbolic link handling behavior in Windows Installer. System administrators should also implement strict software installation policies that limit the ability of users to execute MSI packages from untrusted sources. Additional mitigations include configuring application whitelisting solutions to restrict which installation packages can be executed, monitoring for unusual installation activities through endpoint detection and response tools, and implementing network-based controls to prevent access to known malicious domains. From an ATT&CK framework perspective, this vulnerability maps to technique T1068, which covers 'Exploitation for Privilege Escalation', and T1547.001, which covers 'Registry Run Keys / Startup Folder' as attackers may attempt to establish persistence after exploiting this vulnerability. The vulnerability also relates to T1059, 'Command and Scripting Interpreter', as exploitation may involve executing malicious commands through the elevated privileges gained. Organizations should also consider implementing behavioral monitoring solutions that can detect anomalous symbolic link resolution patterns and installation activities that deviate from normal baseline behavior, as these detection capabilities can provide early warning of potential exploitation attempts.