ZDI-26-621: Microsoft Windows UMPDDrvRealizeBrush Improper Object Management Local Privilege Escalation Vulnerability

Zerodayinitiative • September 8, 2026

This vulnerability allows local attackers to escalate privileges on affected installations of Microsoft Windows. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the win32kfull driver. The issue results from improper management of surface objects during calls to user-mode drivers. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM.

Microsoft has issued an update to correct this vulnerability. More details can be found at:

2026-05-11 - Vulnerability reported to vendor

2026-09-08 - Coordinated public release of advisory

2026-09-08 - Advisory Updated

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Multiple Local Privilege Escalation Vulnerabilities in Microsoft Windows Four local privilege escalation vulnerabilities have been identified in Microsoft Windows, all stemming from improper object management within the win32kfull driver. These vulnerabilities, identified as ZDI-26-618, ZDI-26-619, ZDI-26-620, and ZDI-26-621, allow local attackers to escalate privileges and execute arbitrary code in the context of SYSTEM. An attacker must first execute low-privileged code to exploit these vulnerabilities. Microsoft has issued updates to correct these issues. The vulnerabilities were reported to the vendor on May 11, 2026, and the advisories were publicly released on September 8, 2026. The affected systems are various installations of Microsoft Windows. The vulnerabilities have not been reported as actively exploited in the wild. 4 sources 45

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ZDI-26-621: Microsoft Windows UMPDDrvRealizeBrush Improper Object Management Local Privilege Escalation Vulnerability

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