CVE-2025-59259 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically within the Local Session Manager (LSM) component. The root cause is improper validation of the specified type of input, classified under CWE-1287. This flaw allows an authorized attacker—meaning one with some level of local privileges—to send malformed or unexpected input to the LSM over the network, resulting in a denial of service condition. The denial of service could manifest as a crash or hang of the LSM service, which is responsible for managing user sessions and related network connections. The vulnerability has a CVSS 3.1 base score of 6.5, indicating medium severity. The vector metrics indicate network attack vector (AV:N), low attack complexity (AC:L), required privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), but high impact on availability (A:H). The exploitability is considered moderate due to the need for local privileges, but no user interaction is required, and the attack can be performed remotely over the network. There are no known exploits in the wild at the time of publication, and no patches have been linked yet. The vulnerability was reserved in September 2025 and published in October 2025. The improper input validation could be exploited by attackers to disrupt services dependent on LSM, potentially affecting session management and network connectivity on affected systems.

For European organizations, the primary impact of CVE-2025-59259 is the potential for denial of service attacks that disrupt availability of Windows 10 Version 1809 systems. This can affect enterprise environments where LSM is critical for managing user sessions, including remote desktop services, terminal servers, and other networked session-dependent applications. Disruption could lead to downtime, loss of productivity, and potential cascading effects on dependent services. Critical infrastructure sectors such as finance, healthcare, and government agencies relying on this OS version could experience operational interruptions. Since confidentiality and integrity are not impacted, data breaches are unlikely, but service availability degradation can still cause significant operational risk. The requirement for local privileges limits the attack surface somewhat, but insider threats or compromised internal accounts could exploit this vulnerability. The lack of known exploits reduces immediate risk but does not eliminate the threat as attackers may develop exploits post-disclosure.

1. Apply security patches promptly once Microsoft releases them for Windows 10 Version 1809 to address this vulnerability. 2. Restrict local administrative and privileged access to systems running this OS version to minimize the risk of authorized attackers exploiting the flaw. 3. Monitor the stability and logs of the Local Session Manager service for unusual crashes or restarts that could indicate exploitation attempts. 4. Employ network segmentation and access controls to limit exposure of vulnerable systems to untrusted networks or users. 5. Consider upgrading affected systems to a more recent, supported Windows version where this vulnerability is not present or has been fixed. 6. Implement endpoint detection and response (EDR) solutions to identify anomalous behavior related to LSM or session management. 7. Conduct regular security awareness training to reduce insider threat risks and ensure proper privilege management. 8. Use application whitelisting and least privilege principles to reduce the attack surface on critical systems.