Windows AppX Deployment Service Vulnerability (CVE-2025-48820): Privilege Escalation via Improper Link Resolution

Introduction

The Windows AppX Deployment Service, critical for managing Universal Windows Platform (UWP) applications, has once again become the focal point of security concerns. CVE-2025-48820 highlights a severe privilege escalation vulnerability, allowing attackers with minimal local access to gain SYSTEM-level privileges. This flaw underscores persistent challenges in Microsoft's handling of symbolic and hard links, posing significant risks to enterprise environments.

Technical Information

The vulnerability, classified under CWE-59 (Improper Link Resolution Before File Access), occurs due to the AppX Deployment Service's inadequate validation of symbolic or hard links during file operations. Specifically, the service does not sufficiently verify the destination of links before accessing files, enabling attackers to exploit this oversight in a TOCTOU attack scenario.

An attacker can exploit this vulnerability by:

Creating a malicious symbolic link pointing to a sensitive system file, such as C:\Windows\System32\config\SAM.
Triggering the AppX Deployment Service to process this symbolic link during normal application deployment or update operations.
Redirecting the service's privileged operations to the targeted sensitive file, thereby gaining unauthorized SYSTEM-level access.

This attack vector requires local access, limiting remote exploitation but providing a potent method for lateral movement within compromised environments.

Patch Information

Microsoft has released a security update to address a vulnerability identified as CVE-2025-48819. This update is part of the July 2025 security updates for Windows 11. The patch modifies the affected system components to prevent potential exploitation of the vulnerability. Users are advised to install the latest security updates to ensure their systems are protected.

Patch sources:

Affected Systems and Versions

Windows 10 (versions 1809 and later)
Windows 11 (versions 22H2 and later)
Windows Server 2019
Windows Server 2022

These versions are specifically vulnerable due to the implementation of the AppX Deployment Service.

Vendor Security History

Microsoft has previously encountered similar vulnerabilities in the AppX Deployment Service, notably:

CVE-2019-0841: Hard-link mishandling
CVE-2019-1064: Symbolic-link validation failure
CVE-2019-1130: Improper link resolution

These historical vulnerabilities indicate a recurring security gap in Microsoft's handling of symbolic and hard links, emphasizing the need for architectural improvements.

References

Source: This report was created using AI

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An in-depth technical analysis of CVE-2025-48820, a privilege escalation vulnerability in Windows AppX Deployment Service due to improper link resolution.