CVE-2019-1476 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-2019-1483.
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Analysis
by VulDB Data Team • 10/07/2025
The vulnerability described in CVE-2019-1476 represents a critical elevation of privilege flaw within the Windows operating system's AppX Deployment Service component. This vulnerability specifically affects the AppXSVC service which is responsible for managing the installation, updating, and removal of universal Windows platform applications. The flaw arises 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 vulnerability is particularly concerning because it leverages the legitimate system service infrastructure to execute malicious code with elevated privileges, making it difficult to detect through conventional security measures.
The technical implementation of this vulnerability stems from the AppXSVC service's inadequate validation of hard link creation and manipulation during AppX package processing operations. When the service processes certain AppX packages, it fails to properly validate or sanitize hard link references, allowing an attacker to create malicious hard links that point to protected system files or directories. This improper handling creates a race condition or path traversal scenario where the service inadvertently executes code from attacker-controlled locations. The vulnerability is classified under CWE-22 as a "Path Traversal" and CWE-787 as "Out-of-bounds Write," representing multiple attack vectors that can be exploited to gain unauthorized system access. The flaw exists in the Windows AppX deployment service implementation where it does not properly validate the integrity of file system references when processing application packages.
The operational impact of this vulnerability is severe as it allows attackers to execute arbitrary code with system-level privileges without requiring any special authentication or prior access to the target system. Once exploited, an attacker can gain complete control over the affected Windows system, enabling them to install malware, modify system files, establish persistence mechanisms, and access sensitive data. The vulnerability affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, making it a widespread concern for enterprise environments. Attackers can exploit this vulnerability through various means including malicious AppX packages delivered via phishing emails, compromised software distribution channels, or by leveraging other initial access vectors to establish a foothold before attempting privilege escalation. This vulnerability is particularly dangerous in enterprise environments where users may have legitimate access to install applications but should not be able to escalate to system privileges.
The exploitation of CVE-2019-1476 aligns with several tactics described in the MITRE ATT&CK framework, particularly the privilege escalation techniques under T1068 and the persistence mechanisms under T1059. The vulnerability can be leveraged as part of a broader attack chain where initial access is gained through social engineering or other means, followed by privilege escalation to achieve system compromise. Security researchers have noted that this vulnerability can be particularly challenging to detect because the exploitation occurs within legitimate system services, making it appear as normal system behavior to traditional monitoring tools. Organizations should implement immediate mitigations including applying Microsoft security updates, restricting user privileges, and monitoring for unusual hard link creation activities within system directories. The vulnerability demonstrates the importance of proper input validation and file system security controls in service implementations, particularly those handling user-supplied content or packages. Organizations should also consider implementing additional security measures such as AppLocker policies to restrict the installation of unsigned or untrusted applications, and deploy behavioral monitoring solutions that can detect anomalous hard link creation patterns that may indicate exploitation attempts.