CVE-2020-0733 in Malicious Software Removal Tool
Summary
by MITRE
An elevation of privilege vulnerability exists when the Windows Malicious Software Removal Tool (MSRT) improperly handles junctions.To exploit this vulnerability, an attacker would first have to gain execution on the victim system, aka 'Windows Malicious Software Removal Tool Elevation of Privilege Vulnerability'.
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Analysis
by VulDB Data Team • 03/30/2024
The vulnerability identified as CVE-2020-0733 represents a critical elevation of privilege flaw within the Windows Malicious Software Removal Tool, a component designed to detect and remove malicious software from Windows systems. This vulnerability stems from the MSRT's improper handling of symbolic links and junction points within the Windows file system, creating a path for malicious actors to escalate their privileges beyond the intended security boundaries. The flaw exists in the way the tool processes file system junctions during its operation, allowing attackers to manipulate the tool's execution flow through carefully crafted file system structures.
The technical implementation of this vulnerability involves the MSRT's failure to properly validate or sanitize file system junctions when processing system components. When the tool encounters a junction point in its scanning or removal process, it does not adequately verify the target location or validate the integrity of the junction itself. This improper handling creates a condition where an attacker can establish a malicious junction that points to a privileged system location, enabling the tool to execute code with elevated privileges when it attempts to process what it believes to be a legitimate file system element. The vulnerability specifically manifests when the MSRT processes files or directories that are actually junction points redirecting to protected system areas, bypassing normal access controls.
The operational impact of this vulnerability is significant as it allows attackers who have already achieved initial system compromise to escalate their privileges without requiring additional attack vectors. The attack scenario typically begins with an attacker gaining user-level access through various means such as phishing, drive-by downloads, or other initial compromise techniques. Once the attacker has established a foothold, they can leverage this vulnerability by creating a malicious junction that the MSRT will process, thereby executing code with system-level privileges. This creates a particularly dangerous situation because the MSRT is typically executed with elevated privileges as part of Windows security operations, making it an attractive target for privilege escalation. The vulnerability essentially transforms a security tool designed to protect the system into a potential vector for privilege elevation, undermining the trust model that security tools are supposed to maintain.
This vulnerability aligns with CWE-78: Improper Neutralization of Special Elements used in OS Commands, as the MSRT fails to properly handle special file system elements that could be manipulated to alter the tool's behavior. Additionally, it maps to ATT&CK technique T1068: Exploitation for Privilege Escalation, where adversaries leverage vulnerabilities in system components to gain higher privileges. The flaw also demonstrates characteristics of T1548.002: Abuse of Sudo Rights, in that it allows for privilege escalation through legitimate system tools. Organizations should consider this vulnerability in their overall security posture as it represents a critical weakness in Windows' built-in security mechanisms. The remediation approach requires immediate patching of the MSRT component through Windows Update, along with monitoring for suspicious junction creation patterns and implementing strict file system access controls to prevent unauthorized junction manipulation. Security teams should also consider implementing additional monitoring for MSRT execution patterns and ensure that system administrators regularly review file system junctions for potential malicious configurations.