CVE-2025-21347 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically within the Windows Deployment Services (WDS) component. The issue is categorized under CWE-59, which refers to improper link resolution before file access, commonly known as 'link following'. This vulnerability arises when WDS improperly handles symbolic links or junction points before accessing files, potentially allowing an attacker to manipulate the file system path resolution process. The consequence of this flaw is a denial of service (DoS) condition, where the attacker can cause the WDS service to crash or become unresponsive, disrupting deployment operations. The CVSS v3.1 base score is 6.0 (medium severity), with the vector indicating local attack vector (AV:L), high attack complexity (AC:H), low privileges required (PR:L), and user interaction needed (UI:R). The scope remains unchanged (S:U), and the impact affects integrity and availability (I:H/A:H) but not confidentiality (C:N). No known exploits have been reported in the wild as of the publication date. The vulnerability was reserved in December 2024 and published in February 2025. No patches were linked at the time of reporting, suggesting organizations should monitor for updates from Microsoft. The vulnerability primarily affects systems running the specific build 10.0.17763.0 of Windows 10 Version 1809, which is an older release but may still be in use in some enterprise environments. Exploitation requires local access and user interaction, limiting remote exploitation but still posing a risk in environments where users have local access to WDS servers or deployment workstations.

For European organizations, the impact of CVE-2025-21347 centers on the potential disruption of Windows Deployment Services, which are often used for network-based installation and deployment of Windows operating systems. A successful denial of service attack could halt deployment operations, delaying system provisioning and updates, which is critical in large enterprises and public sector organizations. This disruption can affect operational continuity, especially in sectors relying on rapid deployment or recovery, such as healthcare, finance, and government. Although confidentiality is not impacted, the integrity and availability of deployment services are at risk, potentially leading to increased downtime and administrative overhead. Organizations still running Windows 10 Version 1809, particularly those that have not migrated to newer Windows versions, face higher exposure. The requirement for local access and user interaction reduces the risk of widespread remote attacks but does not eliminate insider threats or attacks originating from compromised local accounts. The absence of known exploits in the wild provides some reprieve but should not lead to complacency.

1. Monitor Microsoft security advisories closely and apply official patches or updates as soon as they become available for Windows 10 Version 1809 and WDS components. 2. Restrict local user permissions on WDS servers to minimize the number of users who can interact with the deployment services and potentially exploit the vulnerability. 3. Implement strict access controls and auditing on systems running WDS to detect unusual activities or attempts to exploit symbolic link handling. 4. Consider upgrading affected systems to a supported and more recent Windows version where this vulnerability is not present or has been addressed. 5. Educate local users with access to WDS about the risks of interacting with suspicious files or links and enforce policies to limit user interaction with untrusted content. 6. Use application whitelisting and endpoint protection solutions to detect and prevent exploitation attempts involving file system manipulation. 7. Regularly review and harden deployment infrastructure configurations to reduce attack surface and improve resilience against DoS conditions.