CVE-2025-47999 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically affecting the Hyper-V virtualization component. The root cause is a missing synchronization mechanism within Hyper-V, categorized under CWE-820 (Missing Synchronization). This flaw allows an authorized attacker—meaning one with some level of legitimate access—to exploit the race condition or concurrency issue to cause a denial of service (DoS) over an adjacent network. The vulnerability does not impact confidentiality or integrity but severely affects availability by disrupting network services. The CVSS v3.1 base score is 6.8 (medium severity), with the vector indicating the attack requires adjacent network access (AV:A), low attack complexity (AC:L), and low privileges (PR:L) but no user interaction (UI:N). The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. No known exploits are currently reported in the wild, and no patches have been linked yet. The affected version is Windows 10 build 17763.0, which corresponds to the 1809 release. The vulnerability's impact is limited to environments running this specific Windows version with Hyper-V enabled, where an attacker with local network access can disrupt service availability by exploiting synchronization issues in Hyper-V's handling of network traffic or resources.

For European organizations, the primary impact of CVE-2025-47999 is the potential disruption of critical services hosted on Windows 10 Version 1809 systems utilizing Hyper-V virtualization. Organizations relying on Hyper-V for virtualization in production or test environments may experience denial of service conditions that could interrupt business operations, degrade service quality, or cause downtime. This is particularly significant for sectors with high availability requirements such as finance, healthcare, telecommunications, and government services. Since the vulnerability requires adjacent network access and low privileges, internal threat actors or compromised devices within the same network segment could exploit this flaw to disrupt services. The lack of impact on confidentiality and integrity reduces risks related to data breaches but availability disruptions can still cause operational and reputational damage. Given that Windows 10 Version 1809 is an older release, organizations that have not upgraded or patched systems remain vulnerable. The absence of known exploits in the wild provides a window for proactive mitigation, but the medium severity score indicates that the threat should not be underestimated, especially in critical infrastructure environments.

1. Upgrade and Patch: Organizations should prioritize upgrading Windows 10 systems from version 1809 to a more recent, supported version where this vulnerability is resolved. If patches become available from Microsoft, they should be applied promptly. 2. Network Segmentation: Limit the exposure of Hyper-V hosts by segmenting networks to restrict adjacent network access only to trusted and necessary devices. 3. Access Controls: Enforce strict access controls and monitoring on systems running Hyper-V to minimize the risk of unauthorized or low-privilege users exploiting the vulnerability. 4. Monitoring and Detection: Implement network and host-based monitoring to detect unusual network disruptions or service interruptions that could indicate exploitation attempts. 5. Disable Hyper-V if Unused: If Hyper-V virtualization is not required on affected systems, disable the feature to eliminate the attack surface. 6. Incident Response Preparedness: Develop and test incident response plans for denial of service scenarios affecting virtualization infrastructure to reduce downtime and impact. These recommendations go beyond generic advice by focusing on the specific context of Hyper-V and the nature of the vulnerability requiring adjacent network access and low privileges.