Critical Microsoft Vulnerability CVE-2026-3929 Allows Remote Code Execution

Microsoft has released emergency security updates addressing CVE-2026-3929, a critical remote code execution vulnerability affecting multiple Windows and Office products. The vulnerability carries a CVSS score of 9.8 and requires immediate attention from all organizations using affected software.

Attackers could exploit this vulnerability by sending specially crafted requests to affected systems. Successful exploitation could allow remote attackers to execute arbitrary code with SYSTEM privileges. No user interaction is required for exploitation in server scenarios.

Affected Products:

• Windows 10 (Version 21H2 and later)
• Windows 11 (All versions)
• Microsoft Office 2019 and 365
• Windows Server 2019 and 2022
• Microsoft Exchange Server 2019 and 2022

The vulnerability exists in the way Microsoft Windows handles objects in memory. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take complete control of the affected system.

Microsoft has released security updates to address this vulnerability. Organizations should apply these updates immediately. The updates are available through the Microsoft Security Response Center website and Windows Update.

For systems that cannot be patched immediately, Microsoft recommends implementing workarounds including:

• Blocking TCP ports 80 and 443 at network boundaries
• Implementing application layer firewalls
• Restricting access to affected services

The vulnerability was discovered by security researchers at Redmond Security Labs and responsibly disclosed to Microsoft. Microsoft has confirmed that there are no known public exploits targeting this vulnerability at the time of release.

Organizations should test updates in a non-production environment before deployment to minimize potential disruption. Critical infrastructure organizations should coordinate patch deployment with their IT security teams.

For detailed information on affected products and update procedures, refer to the Microsoft Security Guide and the official CVE entry.

This security update is part of Microsoft's monthly Patch Tuesday cycle for June 2026. Organizations should also review other security updates released in this cycle to ensure comprehensive protection against known vulnerabilities.