CVE-2025-48799 is a high-severity vulnerability affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0) specifically within the Windows Update Service. The vulnerability is classified under CWE-59, which pertains to improper link resolution before file access, commonly referred to as 'link following'. This flaw allows an authorized local attacker to exploit the way the Windows Update Service resolves symbolic links or junction points before accessing files. By manipulating these links, an attacker can cause the service to access unintended files or directories, potentially leading to privilege escalation. The attacker requires local access with limited privileges (PR:L) and no user interaction (UI:N) is needed to exploit the vulnerability. The vulnerability impacts confidentiality, integrity, and availability (all rated high), indicating that successful exploitation could allow an attacker to gain elevated privileges, modify or access sensitive files, or disrupt system operations. The CVSS v3.1 base score is 7.8, reflecting a high severity with low attack complexity (AC:L) but requiring local access (AV:L). No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may rely on workarounds or system hardening until official updates are released. The vulnerability's root cause is the improper handling of symbolic links by the Windows Update Service, which can be exploited to redirect file operations to unauthorized locations, thereby bypassing intended security controls and elevating privileges.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and government entities still operating legacy systems or those that have not upgraded beyond Windows 10 Version 1809. Successful exploitation could allow attackers with limited local access—such as through compromised user accounts or insider threats—to escalate privileges to SYSTEM level, potentially gaining full control over affected machines. This could lead to unauthorized access to sensitive data, disruption of critical update processes, and the deployment of malicious payloads with elevated rights. Given the role of the Windows Update Service in maintaining system security, exploitation could also hinder patch management, leaving systems vulnerable to further attacks. Organizations in sectors with strict regulatory requirements for data protection (e.g., finance, healthcare, public administration) may face compliance risks and reputational damage if this vulnerability is exploited. Additionally, the lack of user interaction required for exploitation increases the risk of automated or stealthy attacks within internal networks.

1. Immediate mitigation should focus on restricting local access to systems running Windows 10 Version 1809, ensuring that only trusted users have login privileges. 2. Employ application whitelisting and endpoint protection solutions that can detect and block suspicious symbolic link manipulations or unauthorized privilege escalation attempts. 3. Monitor system logs and Windows Update Service activities for unusual file access patterns or errors indicative of link following exploitation attempts. 4. Disable or restrict the Windows Update Service where feasible in controlled environments until patches are available, or configure it to run with the least privileges necessary. 5. Implement strict file system permissions to limit the creation and manipulation of symbolic links by non-administrative users. 6. Prepare for patch deployment by establishing an asset inventory to identify all affected systems and prioritize their remediation. 7. Educate IT staff and users about the risks of local privilege escalation and enforce strong local account management policies. 8. Consider upgrading affected systems to newer supported Windows versions where this vulnerability is not present or has been patched.