CVE-2025-49751 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically within the Hyper-V virtualization platform. The root cause is a missing synchronization mechanism, classified under CWE-820 (Missing Synchronization), which leads to a race condition or concurrency flaw. This flaw allows an authorized attacker—meaning one with some level of local privileges—to induce a denial of service condition on an adjacent network segment. The attack vector is adjacent network (AV:A), indicating the attacker must be on the same or a directly connected network segment. The vulnerability has low attack complexity (AC:L), requires privileges (PR:L) but no user interaction (UI:N), and affects availability (A:H) without impacting confidentiality or integrity. The scope is changed (S:C), meaning the vulnerability can affect resources beyond the initially compromised component. The CVSS v3.1 base score is 6.8, reflecting a medium severity rating. No known exploits have been reported in the wild, and no patches have been released at the time of publication. The vulnerability could be exploited to disrupt network services, potentially impacting virtualized environments that rely on Hyper-V for network connectivity and isolation. The absence of synchronization suggests that concurrent operations within Hyper-V's network handling code can be manipulated to cause service interruptions or crashes, leading to denial of service on adjacent network segments. This can affect virtual machines and services dependent on Hyper-V networking, potentially causing downtime or degraded performance.

For European organizations, the primary impact of CVE-2025-49751 is the potential disruption of network availability within virtualized environments using Hyper-V on Windows 10 Version 1809. Organizations relying on Hyper-V for critical infrastructure, such as data centers, cloud services, or internal virtualization, may experience denial of service conditions that interrupt business operations. This can lead to downtime, loss of productivity, and potential cascading effects on dependent services. Since the vulnerability requires local privileges and adjacency, insider threats or compromised internal systems pose the greatest risk. The lack of impact on confidentiality and integrity limits data breach concerns but does not reduce the operational risk. Sectors with high virtualization adoption, including finance, manufacturing, and public administration, could face significant operational challenges. Additionally, the medium severity and absence of known exploits suggest a window for proactive mitigation before exploitation becomes widespread.

Given the absence of an official patch, European organizations should implement several specific mitigations: 1) Restrict and monitor access to systems running Windows 10 Version 1809 with Hyper-V enabled, ensuring only trusted and authorized personnel have local privileges. 2) Limit network adjacency exposure by segmenting networks and applying strict firewall rules to reduce the attack surface from adjacent networks. 3) Disable Hyper-V on systems where virtualization is not required to eliminate the vulnerable component. 4) Employ robust monitoring and alerting for unusual network disruptions or Hyper-V service crashes that could indicate exploitation attempts. 5) Plan and prioritize upgrading affected systems to newer Windows versions with security updates once patches are released. 6) Conduct internal audits to identify all systems running the affected version and assess their criticality and exposure. 7) Educate IT staff about the vulnerability and encourage rapid incident response readiness. These targeted actions go beyond generic advice by focusing on access control, network segmentation, and proactive system inventory and monitoring tailored to this specific vulnerability.