CVE-2025-48820 is a high-severity local privilege escalation vulnerability affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability arises from improper link resolution before file access, specifically within the Windows AppX Deployment Service. This service is responsible for managing the deployment and installation of Windows Store applications (AppX packages). The flaw is categorized under CWE-59, which involves 'Improper Link Resolution Before File Access,' commonly known as 'link following.' In this context, the vulnerability allows an authorized attacker with limited privileges on the affected system to exploit the improper handling of symbolic links or junction points by the AppX Deployment Service. By manipulating these links, the attacker can cause the service to access or modify files in unintended locations, thereby escalating their privileges to a higher level, potentially SYSTEM or administrative privileges. The CVSS v3.1 base score is 7.8, indicating a high severity. The vector indicates that the attack requires local access (AV:L), low attack complexity (AC:L), privileges required are low (PR:L), no user interaction (UI:N), and impacts confidentiality, integrity, and availability at a high level (C:H/I:H/A:H). The scope remains unchanged (S:U). No known exploits in the wild have been reported yet, and no patches are currently linked, suggesting that mitigation may rely on vendor updates or workarounds once available. This vulnerability is significant because it can be exploited by an attacker who already has some level of access to the system to gain full control, potentially leading to complete system compromise, unauthorized data access, or disruption of services.

For European organizations, this vulnerability poses a substantial risk, especially in environments where Windows 10 Version 1809 is still in use. The ability for a local attacker to escalate privileges can lead to unauthorized access to sensitive data, disruption of critical business operations, and potential lateral movement within corporate networks. Industries with strict regulatory requirements, such as finance, healthcare, and government sectors, could face compliance violations if exploited. Additionally, organizations relying on legacy systems or delayed patch management are at higher risk. The lack of known exploits in the wild currently reduces immediate threat levels; however, the high severity and potential impact necessitate proactive measures. Attackers with initial footholds, such as through phishing or insider threats, could leverage this vulnerability to gain elevated privileges, bypass security controls, and deploy malware or ransomware, amplifying the damage. Given the critical nature of confidentiality, integrity, and availability impacts, exploitation could lead to data breaches, operational downtime, and reputational damage.

1. Immediate mitigation should focus on upgrading affected systems to a supported and fully patched version of Windows 10 or later, as Microsoft is expected to release a security update addressing this vulnerability. 2. Until patches are available, restrict local access to systems running Windows 10 Version 1809 by enforcing strict access controls and monitoring for unusual local activity. 3. Implement application whitelisting and restrict the use of symbolic links or junction points by users without administrative privileges to reduce the attack surface. 4. Employ endpoint detection and response (EDR) solutions to detect suspicious behavior related to AppX Deployment Service or privilege escalation attempts. 5. Conduct regular audits of user privileges and remove unnecessary local accounts or rights that could be leveraged by attackers. 6. Educate users and administrators about the risks of local privilege escalation and the importance of applying security updates promptly. 7. Use Group Policy or other configuration management tools to enforce security best practices and limit the ability to create or manipulate symbolic links by non-administrative users. 8. Monitor system logs for anomalies related to file access and link resolution activities within the AppX Deployment Service.