CVE-2025-53803 is a vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) involving the generation of error messages by the Windows kernel that inadvertently contain sensitive information. Classified under CWE-209 (Generation of Error Message Containing Sensitive Information), this flaw allows an attacker with authorized local access to the system to obtain confidential data through error messages. The vulnerability does not require user interaction and has a low attack complexity, meaning that an attacker with limited privileges can exploit it without sophisticated techniques. The CVSS v3.1 base score is 5.5, indicating a medium severity level, primarily due to the high confidentiality impact but no impact on integrity or availability. The scope remains unchanged, meaning the vulnerability affects only the vulnerable component without spreading to other system components. No public exploits or patches have been reported at the time of publication, but the vulnerability is officially recognized and published by Microsoft. The flaw could be leveraged in scenarios where local users or processes seek to escalate their knowledge of system internals or sensitive kernel data, potentially aiding further attacks or privilege escalation attempts. Since the vulnerability is kernel-related, the sensitive information disclosed could include memory contents, kernel pointers, or other data that should remain protected from local users.

For European organizations, the primary impact of CVE-2025-53803 is the potential unauthorized disclosure of sensitive kernel-level information to authorized local users. This could facilitate further attacks such as privilege escalation, targeted exploitation, or lateral movement within networks. Organizations relying on Windows 10 Version 1809, especially in critical infrastructure, government, finance, and healthcare sectors, may face increased risk if attackers leverage this vulnerability to gain deeper system insights. Although the vulnerability does not directly compromise system integrity or availability, the confidentiality breach could expose sensitive operational data or security mechanisms. The requirement for local access limits remote exploitation but does not eliminate risk in environments with multiple users or where attackers have gained initial footholds. The absence of known exploits reduces immediate threat but underscores the need for proactive mitigation. European entities with legacy systems or delayed patching cycles are particularly vulnerable, as Windows 10 Version 1809 is an older release still in use in some environments.

To mitigate CVE-2025-53803, European organizations should first inventory and identify all systems running Windows 10 Version 1809 (build 10.0.17763.0). Restrict local access to trusted users only, employing strict access controls and user account management to minimize the number of authorized local users. Implement robust monitoring and alerting for unusual error message generation or attempts to access kernel-level information. Employ endpoint detection and response (EDR) solutions capable of detecting anomalous local activity that could indicate exploitation attempts. Since no patches are currently linked, organizations should closely monitor Microsoft security advisories and apply any forthcoming updates promptly. Where feasible, consider upgrading affected systems to newer, supported Windows versions with improved security postures. Additionally, conduct regular security awareness training emphasizing the risks of local privilege misuse and enforce the principle of least privilege across all user accounts. Network segmentation can also limit the impact of compromised local accounts by isolating critical systems.