CVE-2020-0896 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists when Windows improperly handles hard links, aka 'Windows Hard Link Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2020-0840, CVE-2020-0841, CVE-2020-0849.
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Analysis
by VulDB Data Team • 04/11/2024
The vulnerability described in CVE-2020-0896 represents a critical elevation of privilege flaw within the Windows operating system's handling of hard links. This issue specifically manifests when the Windows kernel fails to properly validate or restrict the creation and manipulation of hard links, creating a pathway for malicious actors to escalate their privileges from standard user level to system level access. The vulnerability is particularly concerning because hard links are fundamental filesystem constructs that allow multiple directory entries to point to the same file data, and their improper handling can lead to unauthorized access to protected system resources.
The technical exploitation of this vulnerability involves leveraging the Windows filesystem's inadequate validation mechanisms for hard link operations. When a malicious user creates or manipulates hard links inappropriately, they can potentially bypass security restrictions that should normally prevent access to protected files or directories. This flaw operates at the kernel level within the Windows subsystem, making it particularly dangerous as it can be exploited to gain elevated privileges without requiring administrative credentials or specific user permissions. The vulnerability's impact is amplified by the fact that hard links are commonly used in legitimate system operations, making the exploitation less obvious to security monitoring systems.
From an operational perspective, this vulnerability creates significant risk for Windows environments as it allows attackers to escalate privileges without complex exploitation techniques. The attack surface is broad since hard links are used throughout the Windows filesystem for various legitimate purposes including backup operations, system recovery, and file management. Security professionals must consider that this vulnerability could be exploited by adversaries to gain system-level access, potentially leading to complete system compromise, data exfiltration, or persistence mechanisms. The vulnerability's classification under CWE-264 indicates it involves improper privilege management, while its operational characteristics align with techniques described in the ATT&CK framework under privilege escalation tactics and techniques.
Organizations should implement immediate mitigations including applying the relevant Microsoft security updates that address the hard link handling mechanisms in the Windows kernel. System administrators should also consider monitoring for unusual hard link creation patterns and implementing least privilege access controls to limit potential exploitation. The vulnerability demonstrates the importance of proper filesystem access control implementation and highlights the need for comprehensive security testing of core operating system components. Additionally, security teams should review existing endpoint protection solutions to ensure they can detect anomalous hard link behavior that might indicate exploitation attempts. The remediation process requires careful attention to ensure that legitimate system operations continue to function properly while closing the security gap that allows privilege escalation through improper hard link handling.