CVE-2025-59259 is a vulnerability classified under CWE-1287 (Improper Validation of Specified Type of Input) affecting the Windows Local Session Manager (LSM) component in Windows 10 Version 1809 (build 10.0.17763.0). The flaw arises because LSM does not correctly validate the type of input it receives over the network, allowing an attacker with authorized access to send specially crafted input that causes the service to fail, resulting in a denial of service condition. The attack vector is network-based (AV:N), with low attack complexity (AC:L), requiring privileges (PR:L) but no user interaction (UI:N). The scope remains unchanged (S:U), and the impact is limited to availability (A:H) with no confidentiality or integrity impact. The vulnerability was published on October 14, 2025, and no known exploits have been reported yet. The improper input validation could cause the LSM service to crash or become unresponsive, disrupting session management and potentially affecting dependent services and applications. Since LSM is critical for managing user sessions and authentication tokens, its disruption can lead to service outages or degraded system functionality. The vulnerability is particularly relevant for environments where Windows 10 Version 1809 is still in use, especially in networked or enterprise settings where session management is critical.

For European organizations, this vulnerability poses a risk primarily to system availability. Disruption of the Local Session Manager can lead to denial of service conditions affecting user sessions, authentication processes, and potentially dependent applications and services. This can cause operational downtime, impacting business continuity and productivity. Sectors such as finance, healthcare, government, and critical infrastructure that rely on stable Windows session management are particularly vulnerable. Since the attack requires authorized access, insider threats or compromised credentials could be leveraged to exploit this vulnerability. The lack of confidentiality or integrity impact reduces the risk of data breaches but does not mitigate the operational risks associated with service disruption. Organizations with legacy systems still running Windows 10 Version 1809 are at higher risk, especially if these systems are exposed to network access without adequate segmentation or controls.

1. Apply security patches from Microsoft as soon as they become available to address this vulnerability. 2. Restrict network access to the Local Session Manager service by implementing strict firewall rules and network segmentation, limiting exposure to trusted hosts only. 3. Monitor network traffic and system logs for unusual or malformed input targeting LSM or signs of service instability. 4. Enforce the principle of least privilege to minimize the number of users with authorized access capable of exploiting this vulnerability. 5. Consider upgrading affected systems to a more recent, supported version of Windows 10 or Windows 11 where this vulnerability is not present. 6. Implement robust credential management and multi-factor authentication to reduce the risk of unauthorized access. 7. Conduct regular vulnerability assessments and penetration testing focusing on session management components to detect similar issues proactively.