CVE-2020-0786 in Windows
Summary
by MITRE
A denial of service vulnerability exists when the Windows Tile Object Service improperly handles hard links, aka 'Windows Tile Object Service Denial of Service Vulnerability'.
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Analysis
by VulDB Data Team • 04/10/2024
The Windows Tile Object Service vulnerability CVE-2020-0786 represents a critical denial of service weakness that affects multiple Windows operating systems including Windows 10 version 1903 and 1909, Windows Server 2019, and Windows Server 2016. This vulnerability specifically targets the Windows Tile Object Service which is responsible for managing tile objects in the Windows shell environment, particularly those used in the Start menu and taskbar. The flaw manifests when the service processes hard links inappropriately, creating a condition where legitimate system operations can be disrupted through maliciously crafted file structures.
The technical root cause of this vulnerability lies in the improper handling of hard links within the Windows Tile Object Service implementation. Hard links are file system objects that provide multiple directory entries pointing to the same file data on disk. When the Tile Object Service encounters certain combinations of hard links in tile object configurations, it fails to properly validate or process these references, leading to a system crash or complete service unavailability. This issue falls under the CWE-119 weakness category, which encompasses improper access to memory locations, and specifically relates to improper handling of file system objects. The vulnerability enables attackers to craft malicious file structures that when processed by the Tile Object Service, trigger a denial of service condition that can affect system stability and user access to desktop functionality.
The operational impact of CVE-2020-0786 extends beyond simple service disruption as it can severely compromise user productivity and system availability. When exploited, the vulnerability allows an attacker to cause the Windows Tile Object Service to crash repeatedly, resulting in a degraded user experience where the Start menu becomes unresponsive, taskbar functionality is impaired, and overall system stability is compromised. This vulnerability can be particularly dangerous in enterprise environments where multiple users rely on consistent desktop functionality, as it can be leveraged to disrupt operations across multiple workstations simultaneously. The attack vector typically involves creating specially crafted hard link structures that, when accessed through the Windows shell, trigger the service crash. This vulnerability aligns with ATT&CK technique T1499.001 which covers network denial of service attacks, and T1566.001 which involves spearphishing attachments that could contain malicious hard link structures designed to exploit this weakness.
Mitigation strategies for CVE-2020-0786 primarily focus on applying the official Microsoft security updates released as part of the May 2020 Patch Tuesday updates. Organizations should prioritize immediate deployment of the relevant security patches to address the vulnerability at the source. Additionally, system administrators can implement defensive measures such as monitoring for unusual hard link creation patterns and restricting user access to areas where malicious hard link structures could be created. Network segmentation and access controls can help limit the potential impact of exploitation attempts, while regular system monitoring can detect early signs of service disruption. The vulnerability demonstrates the importance of proper file system object validation and the need for robust input sanitization in Windows system services, particularly those handling user interface elements like tile objects. Security teams should also consider implementing automated patch management systems to ensure timely deployment of security updates across all affected systems and maintain awareness of similar vulnerabilities in other Windows services that may exhibit comparable hard link handling issues.