Microsoft Windows Updates Cause SQL Server Performance Issues

Microsoft has confirmed that Windows updates released since the October 2026 Patch Tuesday are triggering performance and stability issues on systems running SQL Server. The fault stems from linked server queries failing to close connections upon completion, causing open connections to accumulate and progressively degrade server performance. The issue impacts both client operating systems, specifically Windows 10 and Windows 11, and server environments running Windows Server 2012 and later. Microsoft plans to resolve the defect with an out-of-band update in the coming days, advising affected enterprise administrators to request interim mitigations via official business support channels.

Key Facts

What Causes the SQL Server Performance Degradation?

The performance degradation occurs because SQL Server queries leave database connections open after execution finishes. Rather than terminating as expected, these unclosed connections continuously accumulate inside the environment. Over time, the growing volume of idle, lingering connections exhausts system resources, leading to observable operational instability and declining query performance across affected hosts.

According to Microsoft's Windows release health dashboard, the flaw specifically targets SQL Server linked server queries that utilise OLE DB providers to establish communication with external databases. Even when associated queries terminate, administrators observe open connections persisting indefinitely. While administrators can attempt manual termination of these connections or perform an outright restart of the SQL service, Microsoft cautions that doing so may abruptly terminate active transactions without preventing the problem from recurring.

Accumulating unclosed connections from completed linked server queries cause ongoing server stability and performance degradation.

Which Systems and External Connections Are Impacted?

The issue impacts client systems running Windows 10 and Windows 11, alongside server platforms running Windows Server 2012 and newer editions. For database connectivity, Microsoft confirmed that external connections utilising OLE DB providers are vulnerable, with Oracle and PostgreSQL databases identified among the third-party platforms directly affected by the connection-handling defect.

The failure to release connections manifests in mixed-database architectures where SQL Server interacts with foreign endpoints. Administrators monitoring affected infrastructure will see connection counts steadily climb despite queries being inactive. Microsoft has committed to releasing an out-of-band Windows update to permanently correct the behaviour across supported operating systems, whilst offering business support mitigations for impacted organisations.

The connection accumulation bug affects both client and server Windows releases communicating with external databases such as Oracle and PostgreSQL.

What Should You Do?

• Contact Microsoft Support for Business to request a temporary mitigation while awaiting the official fix.
• Prepare to deploy Microsoft's forthcoming out-of-band Windows update scheduled for release over the next few days.
• Manually close lingering external connections or restart the SQL Server service to temporarily restore stability, noting that this may kill active queries and the issue will resurface over time.

Common Questions

Does restarting the SQL Server service provide a permanent fix?

Restarting the SQL service provides only temporary relief by clearing accumulated open connections. However, Microsoft warns that restarting can kill active user queries, and the underlying connection accumulation bug will inevitably resurface as new linked server queries are executed.

Which external database connections are confirmed to be affected?

Microsoft confirmed the issue affects SQL Server linked server queries using OLE DB providers to connect to external databases. Connections to Oracle and PostgreSQL databases are specifically confirmed as affected, with administrators observing increasing open connections even after queries stop running.

Which operating system versions are impacted by the update bug?

The bug impacts both client and server operating systems running updates released since the October 2026 Patch Tuesday. Affected platforms include client installations on Windows 10 and Windows 11, as well as enterprise server deployments on Windows Server 2012 and later.

Sources and Methodology

This dispatch is based exclusively on reporting published by BleepingComputer on November 12, 2026. ROCKSTARmedia Infosec has not reviewed, verified or checked any other document, advisory or vendor page; this dispatch is based only on the source text above.