This vulnerability (CVE-2026-20842) involves a use-after-free condition in the Windows Desktop Window Manager (DWM) on Windows 10 Version 21H2 (build 10.0.19044.0). An authorized attacker with local access can exploit this flaw to elevate their privileges, potentially gaining higher system rights. The CVSS v3.1 base score is 7.0, reflecting high severity with local attack vector, high attack complexity, and requiring low privileges but no user interaction. Microsoft has released an official fix to address this issue.

Successful exploitation of this use-after-free vulnerability can lead to local privilege escalation, allowing an attacker with authorized local access to gain elevated privileges. This can compromise system integrity, confidentiality, and availability as indicated by the high impact on confidentiality, integrity, and availability in the CVSS vector.

An official fix is available from Microsoft for this vulnerability. Users and administrators should apply the security update provided by Microsoft for Windows 10 Version 21H2 (build 10.0.19044.0) as soon as possible to remediate this issue. Refer to the Microsoft security update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20842 for the latest patch information and deployment instructions.