CVE-2020-1467: Windows 10 Privilege Escalation Vulnerability

CVE-2020-1467 Overview

CVE-2020-1467 is an elevation of privilege vulnerability that exists when Windows improperly handles hard links. An attacker who successfully exploits this vulnerability could overwrite a targeted file leading to an elevated status, potentially gaining complete control of an affected system.

To exploit this vulnerability, an attacker would first need to log on to the system with valid credentials. Once authenticated, the attacker could run a specially crafted application that exploits the improper handling of hard links, allowing them to escalate their privileges and take control of the affected system.

Critical Impact

Local attackers with low privileges can escalate to elevated status by exploiting improper hard link handling, potentially gaining full system control across multiple Windows versions including both client and server editions.

Affected Products

• Microsoft Windows 10 (versions 1607, 1809, 1903, 1909, 2004)
• Microsoft Windows 7 SP1
• Microsoft Windows 8.1
• Microsoft Windows RT 8.1
• Microsoft Windows Server 2008 SP2 and R2 SP1
• Microsoft Windows Server 2012 and R2
• Microsoft Windows Server 2016 (including versions 1903, 1909, 2004)
• Microsoft Windows Server 2019

Discovery Timeline

• 2020-08-17 - CVE-2020-1467 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2020-1467

Vulnerability Analysis

This vulnerability stems from the Windows operating system's improper handling of hard links within the file system. Hard links are file system objects that allow multiple directory entries to point to the same underlying file data on disk. When Windows fails to properly validate hard link operations, it creates an opportunity for attackers to manipulate file relationships in unintended ways.

The exploitation mechanism involves a local attacker creating malicious hard links that redirect file operations to protected system files. When privileged processes subsequently interact with these manipulated file system entries, the attacker can cause unauthorized file overwrites, effectively bypassing normal access controls and security boundaries.

This class of vulnerability is particularly dangerous because it allows attackers to corrupt or replace critical system files, security configurations, or other protected resources that would normally be inaccessible to low-privileged users.

Root Cause

The root cause of CVE-2020-1467 lies in insufficient validation when the Windows kernel handles hard link creation and file operations. The operating system fails to adequately verify that the requesting user has appropriate permissions for the target file before allowing hard link operations to proceed. This oversight allows attackers to create symbolic relationships between files they control and protected system resources.

Attack Vector

The attack requires local access to the target system with at least low-level user privileges. The exploitation flow involves:

1. An attacker authenticates to the system with standard user credentials
2. The attacker creates a specially crafted hard link pointing from an attacker-controlled location to a protected target file
3. The attacker triggers a privileged process to perform file operations through the malicious hard link
4. The privileged process inadvertently overwrites or modifies the protected file
5. The attacker achieves elevated privileges through the corrupted file or configuration

The vulnerability does not require user interaction beyond the attacker's own actions, and the attack complexity is low once the attacker has local access to the system.

Detection Methods for CVE-2020-1467

Indicators of Compromise

• Unexpected hard link creation events in system directories or protected file locations
• Privileged processes accessing files through unusual directory paths
• Anomalous file modification timestamps on critical system files
• Evidence of privilege escalation following hard link manipulation activities

Detection Strategies

• Monitor Windows Security Event Logs for suspicious file system operations and hard link creation events (Event IDs 4663, 4656)
• Deploy endpoint detection and response (EDR) solutions capable of detecting privilege escalation attempts and abnormal file system behavior
• Implement file integrity monitoring (FIM) on critical system files and directories
• Use behavioral analysis to detect applications creating unusual hard link patterns

Monitoring Recommendations

• Enable advanced auditing for file system access on sensitive directories
• Configure alerts for hard link creation operations targeting system directories
• Monitor process creation events for applications that may be exploiting this vulnerability
• Implement SentinelOne Singularity platform for real-time detection of privilege escalation attempts

How to Mitigate CVE-2020-1467

Immediate Actions Required

• Apply the August 2020 security updates from Microsoft immediately on all affected systems
• Prioritize patching on systems where users have local access with standard credentials
• Conduct an inventory of all Windows systems to identify vulnerable versions
• Implement network segmentation to limit lateral movement from compromised systems

Patch Information

Microsoft has released security updates to address this vulnerability as part of their August 2020 Patch Tuesday release. The security update corrects how Windows handles hard links, preventing the exploitation of this vulnerability. Patches are available for all affected Windows versions through Windows Update, Windows Server Update Services (WSUS), or the Microsoft Update Catalog.

For detailed patch information and download links, refer to the Microsoft Security Advisory CVE-2020-1467.

Workarounds

• Restrict local logon rights to limit the number of users who can authenticate locally to sensitive systems
• Implement the principle of least privilege to minimize the impact of successful exploitation
• Use application whitelisting to prevent unauthorized applications from executing
• Monitor and restrict the creation of hard links using Windows security policies where operationally feasible

# Example: Review file auditing configuration
auditpol /get /category:"Object Access"

# Enable auditing for file system operations
auditpol /set /subcategory:"File System" /success:enable /failure:enable