CVE-2017-0295 in Windows
Summary
by MITRE
Microsoft Windows 10 1607 and 1703, and Windows Server 2016 allow an authenticated attacker to modify the C:\Users\DEFAULT folder structure, aka "Windows Default Folder Tampering Vulnerability".
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Analysis
by VulDB Data Team • 08/20/2024
The Windows Default Folder Tampering Vulnerability represents a critical privilege escalation flaw affecting Microsoft Windows 10 versions 1607 and 1703, along with Windows Server 2016. This vulnerability stems from insufficient access controls within the operating system's default user directory structure, specifically targeting the C:\Users\DEFAULT folder which serves as the template for new user profiles. The flaw allows authenticated users to manipulate this critical system directory, potentially enabling them to establish persistent access mechanisms or elevate their privileges beyond normal user boundaries. From a cybersecurity perspective, this vulnerability directly violates the principle of least privilege and represents a significant weakness in the Windows security model.
The technical implementation of this vulnerability exploits a design oversight in how Windows handles permissions for the DEFAULT folder structure. When users authenticate to the system, they can leverage specific file system operations to modify the contents of C:\Users\DEFAULT without proper authorization checks. This occurs because the system fails to properly validate access rights when processing certain file operations within this directory hierarchy. The vulnerability is particularly concerning because it allows attackers to modify system templates that are used when creating new user accounts, potentially enabling them to inject malicious components that will persist across user sessions. This flaw aligns with CWE-276, which addresses improper permissions for critical resources, and demonstrates a classic case of inadequate access control mechanisms.
The operational impact of this vulnerability extends beyond simple file modification capabilities, as it provides attackers with a persistent foothold within the system. An authenticated attacker can use this vulnerability to establish backdoors, modify system configuration files, or prepare malicious payloads that will be executed when new user accounts are created. The vulnerability's persistence mechanism makes it particularly dangerous because the modifications remain effective even after system reboots or user session changes. This aligns with ATT&CK technique T1547.001, which covers registry run keys and startup folder modifications, as the compromised DEFAULT folder structure can be leveraged to achieve similar persistence objectives. The vulnerability essentially allows attackers to manipulate the system's baseline user environment, creating a stealthy method for maintaining access.
Mitigation strategies for this vulnerability require immediate patch application through Microsoft's security updates, as the flaw was addressed in subsequent security releases. System administrators should implement comprehensive monitoring of the C:\Users\DEFAULT directory for unauthorized modifications, particularly focusing on changes to system files, registry keys, and executable components. Additional defensive measures include implementing strict access controls using Windows permissions, enabling file integrity monitoring solutions, and conducting regular security audits of user profile templates. Organizations should also consider implementing application whitelisting policies to prevent unauthorized executables from being placed within the DEFAULT folder structure. The vulnerability highlights the importance of maintaining strict separation between user and system directories, and demonstrates the critical need for regular security assessments of default system configurations to prevent similar privilege escalation scenarios.