KB5123065 release notes and known issues

September 8, 2026, KB5123065 Monthly Rollup

Scope: Windows Server 2012. This update record adds version, fix and known-issue context. Its publication date is not a lifecycle boundary.

Summary

Microsoft's September 2026 cumulative security update for Windows Server 2012 Extended Security Updates.

Improvements and security content

Cumulative security and quality improvements for Windows Server 2012.

Known issues

Publisher statement

Known issues are documented. Some organizations experienced Remote Desktop Services instability, including failed RDP connections, sign-in issues, servers hanging at Remote Desktop Configuration, and related management tools becoming unresponsive. Microsoft states that updates released on and after September 14, 2026, including KB5129244, resolve the issue.

Affected products and versions

Products

Windows Server 2012 Extended Security Updates

Affected versions

Windows Server 2012

Fixed versions or updates

KB5129244 or later

Recommended action

Install the latest Windows Server 2012 update, including KB5129244 or a later cumulative update.

Official publisher evidence

MICROSOFTVERIFIED

September 8, 2026, KB5123065 Monthly Rollup

Checked 28 Sep 2026. BlackTree preserves the last verified facts if a later source check is temporarily unavailable.

Open the official publisher source