CVE-2026-20823 is a vulnerability classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) affecting Microsoft Windows 10 Version 1809, specifically build 10.0.17763.0. The vulnerability resides in Windows File Explorer, where an authorized local attacker with low privileges can disclose sensitive information stored or processed by the system. The flaw does not require user interaction, making it easier to exploit once local access is obtained. The CVSS v3.1 score is 5.5 (medium), reflecting that the attack vector is local (AV:L), attack complexity is low (AC:L), privileges required are low (PR:L), and no user interaction is needed (UI:N). The scope remains unchanged (S:U), and the impact is high on confidentiality (C:H) but none on integrity (I:N) or availability (A:N). The vulnerability does not currently have known exploits in the wild, and no official patches have been linked yet. The exposure of sensitive information could include user data, system configuration details, or other confidential files accessible via File Explorer. Since the vulnerability requires local access, it is primarily a risk in environments where attackers can gain physical or remote desktop access with limited privileges. The flaw highlights the importance of securing local accounts and limiting unnecessary access to systems running this Windows version.

For European organizations, the primary impact of CVE-2026-20823 is the potential unauthorized disclosure of sensitive information, which could include personal data, intellectual property, or system configuration details. This can lead to privacy violations, regulatory non-compliance (e.g., GDPR), and potential facilitation of further attacks if attackers leverage disclosed information for privilege escalation or lateral movement. The vulnerability does not affect system integrity or availability, so direct disruption or data manipulation is not a concern. However, the confidentiality breach can undermine trust and lead to reputational damage. Organizations with many endpoints running Windows 10 Version 1809, especially in sectors like finance, healthcare, and government, face higher risks. Since exploitation requires local access, environments with weak endpoint security, shared workstations, or inadequate access controls are more vulnerable. The lack of known exploits currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

1. Upgrade affected systems to a more recent and supported Windows version, as Windows 10 Version 1809 is outdated and may no longer receive security updates. 2. Restrict local access to systems running this version by enforcing strict access controls, including strong authentication and limiting user privileges. 3. Implement endpoint protection solutions that monitor and alert on unusual local activity or attempts to access sensitive files via File Explorer. 4. Use application whitelisting and device control policies to prevent unauthorized software or users from accessing or extracting sensitive data. 5. Conduct regular audits of local user accounts and remove or disable unnecessary accounts to reduce attack surface. 6. Educate users about the risks of unauthorized local access and enforce physical security measures to prevent unauthorized physical access to devices. 7. Monitor security advisories from Microsoft for patches or updates addressing this vulnerability and apply them promptly once available.