CVE-2019-0841 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists when Windows AppX Deployment Service (AppXSVC) improperly handles hard links, aka 'Windows Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0730, CVE-2019-0731, CVE-2019-0796, CVE-2019-0805, CVE-2019-0836.
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Analysis
by VulDB Data Team • 02/07/2025
The vulnerability identified as CVE-2019-0841 represents a critical elevation of privilege flaw within the Windows operating system that specifically targets the AppX Deployment Service component. This service is responsible for managing the installation, updating, and removal of modern Windows applications packaged as AppX containers. The vulnerability stems from improper handling of hard links within the service's file processing mechanisms, creating a pathway for malicious actors to escalate their privileges from standard user level to system level access. The flaw exists in the way AppXSVC processes file operations, particularly when dealing with symbolic and hard links that point to sensitive system locations.
The technical exploitation of this vulnerability involves crafting malicious AppX packages that contain specially constructed hard links designed to manipulate the deployment service's behavior. When the system processes these packages, the AppXSVC service follows the hard link references and performs operations on unintended target files, potentially allowing arbitrary code execution or file modification in protected system directories. This mechanism leverages the inherent trust Windows places in the AppX deployment infrastructure, which operates with elevated privileges to perform system-level operations. The vulnerability specifically affects Windows 10 versions 1803 and 1809, as well as Windows Server 2019, making it particularly dangerous in enterprise environments where these systems are commonly deployed.
The operational impact of CVE-2019-0841 extends beyond simple privilege escalation, as it provides attackers with a persistent foothold within target systems. Once successfully exploited, adversaries can install malicious software, modify system files, access sensitive data, or establish backdoors that persist across system reboots. The vulnerability's exploitation requires minimal user interaction, often occurring during legitimate software installation processes or when users accept default installation prompts. This makes it particularly dangerous in environments where users may not be security-aware or where automated deployment processes are in place. The flaw's classification aligns with CWE-227, which addresses improper handling of hard links in file systems, and relates to ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation'. The vulnerability's potential for abuse increases significantly when combined with other attack vectors, as it provides the necessary elevation to perform more sophisticated malicious activities.
Mitigation strategies for CVE-2019-0841 primarily focus on applying Microsoft's official security patches and updates, which address the core flaw in the AppX Deployment Service's hard link handling. System administrators should ensure that all Windows 10 and Windows Server 2019 systems are updated with the latest security patches, particularly those released in May 2019. Additional protective measures include implementing strict application control policies, disabling unnecessary AppX deployment services, and monitoring for unusual file system operations that might indicate exploitation attempts. Network segmentation and privilege separation can help limit the potential damage if exploitation occurs, while endpoint detection and response solutions should be configured to monitor for suspicious hard link creation patterns. Organizations should also consider implementing the principle of least privilege, ensuring that users only have the minimum necessary permissions to perform their required tasks, thereby limiting the potential impact of successful exploitation.