CVE-2025-53803 is a medium-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The issue stems from the Windows Kernel generating error messages that inadvertently contain sensitive information. This vulnerability is classified under CWE-209, which involves the generation of error messages that disclose sensitive data. An authorized attacker with local access and low privileges (PR:L) can exploit this flaw to gain unauthorized disclosure of sensitive information. The vulnerability does not require user interaction (UI:N) and has a low attack complexity (AC:L), but it is limited to local access (AV:L). The scope is unchanged (S:U), meaning the vulnerability affects only the component where it exists without impacting other components. The CVSS v3.1 base score is 5.5, reflecting a medium severity level primarily due to the confidentiality impact (C:H), with no impact on integrity or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability could allow an attacker to gather sensitive kernel-level information that may aid in further local privilege escalation or other attacks, although it does not directly compromise system integrity or availability. Since the affected version is Windows 10 Version 1809, which is an older release, systems still running this version are at risk if not updated or mitigated.

For European organizations, the primary impact of CVE-2025-53803 lies in the potential leakage of sensitive kernel information to local attackers. This could facilitate subsequent attacks such as privilege escalation or targeted exploitation of other vulnerabilities. Organizations with legacy systems running Windows 10 Version 1809, especially in sectors with high security requirements like finance, healthcare, and critical infrastructure, may face increased risk. The confidentiality breach could lead to exposure of sensitive operational data or system internals, potentially aiding attackers in bypassing security controls. Although the vulnerability requires local access and does not directly affect system availability or integrity, it could be leveraged by insider threats or attackers who have already gained limited access. This makes it particularly relevant for environments with shared workstations, remote desktop access, or insufficient endpoint security controls. The absence of a patch increases the urgency for risk mitigation, especially in regulated industries subject to data protection laws such as GDPR.

1. Upgrade or patch: Organizations should prioritize upgrading affected systems to a supported and fully patched Windows version beyond 1809, as this version is out of mainstream support and lacks official patches for this vulnerability. 2. Restrict local access: Implement strict access controls to limit local user accounts and reduce the number of users with local login capabilities on critical systems. 3. Endpoint protection: Deploy advanced endpoint detection and response (EDR) solutions to monitor for suspicious local activities that could indicate exploitation attempts. 4. Audit and monitoring: Enable detailed auditing of local access and kernel-level events to detect anomalous behavior early. 5. User privilege management: Enforce the principle of least privilege to minimize the number of users with privileges sufficient to exploit this vulnerability. 6. Network segmentation: Isolate legacy systems running Windows 10 Version 1809 from sensitive network segments to reduce the risk of lateral movement. 7. Incident response readiness: Prepare and test incident response plans to quickly address any detected exploitation attempts. 8. Vendor communication: Monitor Microsoft security advisories for official patches or workarounds and apply them promptly once available.