CVE-2025-26651 is a vulnerability identified in Microsoft Windows Server 2022, specifically affecting version 10.0.20348.0. The flaw resides in the Windows Local Session Manager (LSM) component, where an exposed dangerous method or function allows an authorized attacker to perform a denial-of-service (DoS) attack over the network. The vulnerability is classified under CWE-749, which refers to the exposure of dangerous methods or functions that can be exploited to disrupt normal operations. In this case, the attacker must have some level of privileges (PR:L - low privileges) but does not require user interaction (UI:N). The attack vector is network-based (AV:N), meaning the attacker can exploit the vulnerability remotely. The impact is limited to availability (A:H), with no direct confidentiality or integrity impact. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The scope remains unchanged (S:U), meaning the vulnerability affects only the vulnerable component without impacting other components. There are no known exploits in the wild at the time of publication, and no patches have been linked yet. The vulnerability could allow attackers to disrupt services hosted on Windows Server 2022 systems by exploiting the exposed LSM method, potentially causing downtime or degraded service performance in enterprise environments relying on this server OS version.

For European organizations, this vulnerability poses a risk primarily to the availability of critical services hosted on Windows Server 2022 infrastructure. Many enterprises, government agencies, and service providers in Europe utilize Windows Server 2022 for hosting applications, managing identity and access, and running business-critical workloads. A successful DoS attack exploiting this vulnerability could lead to service interruptions, impacting business continuity, customer trust, and regulatory compliance, especially in sectors requiring high availability such as finance, healthcare, and public administration. While the vulnerability does not compromise data confidentiality or integrity, the disruption of services could have cascading effects, including operational delays and potential financial losses. Given the network-based attack vector and low privilege requirement, internal threat actors or compromised accounts could exploit this vulnerability to cause denial of service, making internal security controls and monitoring essential.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Monitor Microsoft’s security advisories closely for the release of official patches or updates addressing CVE-2025-26651 and apply them promptly to all affected Windows Server 2022 systems. 2) Restrict network access to the Windows Local Session Manager service by implementing network segmentation and firewall rules that limit exposure to trusted hosts and administrative networks only. 3) Enforce the principle of least privilege rigorously to minimize the number of accounts with the necessary privileges to exploit this vulnerability. 4) Implement robust monitoring and alerting for unusual activity related to LSM or network service disruptions to detect potential exploitation attempts early. 5) Consider deploying intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalous traffic patterns targeting Windows Server 2022 LSM components. 6) Conduct regular security audits and vulnerability assessments focusing on Windows Server configurations and patch levels to ensure timely remediation. 7) Prepare incident response plans that include procedures for mitigating denial-of-service conditions affecting critical Windows Server infrastructure.