CVE-2026-21222 is a vulnerability identified in Microsoft Windows 10 Version 1607 (build 10.0.14393.0) involving the insertion of sensitive information into kernel log files. This vulnerability is classified under CWE-532, which pertains to the inadvertent inclusion of sensitive data in log files, potentially exposing confidential information. The flaw allows an authorized attacker with local access and low privileges to read sensitive information from kernel logs, which should not normally contain such data. The vulnerability does not require user interaction and has a low attack complexity, meaning it can be exploited relatively easily by a local attacker. The CVSS v3.1 base score is 5.5 (medium), reflecting high confidentiality impact but no impact on integrity or availability. The scope is unchanged, indicating the vulnerability affects only the local system context. No known exploits have been reported in the wild, and no official patches have been linked yet, though the vulnerability was publicly disclosed in February 2026. This issue primarily affects legacy Windows 10 installations that have not been updated or migrated to newer versions, which may still be in use in certain enterprise environments. The vulnerability's root cause is improper handling of sensitive data within the Windows kernel logging mechanism, leading to potential information leakage to any user or process with access to these logs.

For European organizations, the primary impact of CVE-2026-21222 is the risk of sensitive information disclosure from affected Windows 10 Version 1607 systems. This could include exposure of credentials, system configuration details, or other confidential data stored in kernel logs. Such leakage could facilitate further attacks, including privilege escalation or lateral movement within networks. Organizations in regulated sectors such as finance, healthcare, and government are particularly vulnerable due to the sensitivity of their data and strict compliance requirements under GDPR and other regulations. The vulnerability does not directly affect system integrity or availability, so operational disruption is unlikely. However, the confidentiality breach could lead to reputational damage, regulatory penalties, and increased risk of targeted attacks. Since exploitation requires local access with some privileges, insider threats or compromised endpoints pose the greatest risk. Legacy systems still running Windows 10 Version 1607, especially those not regularly patched or upgraded, represent the main attack surface. The lack of known exploits in the wild reduces immediate risk but does not eliminate the potential for future exploitation.

To mitigate CVE-2026-21222, European organizations should prioritize upgrading affected systems from Windows 10 Version 1607 to a supported and patched Windows version, as this vulnerability affects an outdated OS release. Until upgrades are completed, restrict access to kernel log files by enforcing strict file permissions and auditing access to these logs to detect unauthorized reads. Implement the principle of least privilege to limit the number of users and processes with local access rights capable of reading sensitive logs. Employ endpoint detection and response (EDR) solutions to monitor for suspicious local activity indicative of exploitation attempts. Regularly review and sanitize logs to remove sensitive information where feasible. Additionally, conduct user awareness training to reduce insider threat risks and ensure that local accounts are secured with strong authentication mechanisms. Maintain an inventory of legacy systems to identify and remediate vulnerable endpoints promptly. Stay informed on Microsoft’s security advisories for any forthcoming patches or workarounds related to this vulnerability.