Windows Update Leak Causes SQL Server Connection Buildup, Microsoft to Issue Fix

Microsoft has acknowledged that a change in the October 2026 Windows update cycle is causing SQL Server linked server queries to leave connections open after completion. The leakage accumulates over time, leading to performance degradation and occasional instability on both client and server systems. An out-of-band update is slated for release within the next few days, and temporary mitigations are available through Microsoft Support for Business.

• Open connections from linked server queries are piling up, slowing SQL Server over time.
• Affected systems include Windows 10, Windows 11, and Windows Server 2012 and newer.
• Administrators can manually close idle connections or restart the SQL service as a short-term workaround.

What the Bug Actually Does

According to Microsoft’s Windows release health dashboard, the issue originates from linked server queries that use OLE DB providers to reach external databases such as Oracle and PostgreSQL. After a query finishes, the expected behavior is for the connection to close. Instead, the connection remains open, and each subsequent query adds another open link. Over extended periods, the number of open connections can grow large enough to noticeably degrade server performance.

Systems Affected and Impact

The problem spans every Windows version from Windows 10 1809 and Windows Server 2012 up to the latest releases. Microsoft noted that the issue does not affect Windows 11 26H2. The leakage can lead to a range of symptoms: slow query response times, increased memory usage, and in some cases, SQL Server crashes or service restarts. In environments where the “Lock Pages in Memory” policy is enabled, the bug may also trigger crash dumps and memory corruption errors.

How Administrators Can Mitigate the Problem

While Microsoft works on a permanent fix, the company offers a few stop-gap measures. Administrators can identify idle connections and close them manually, which can temporarily relieve load. Restarting the SQL service also restores stability, though it may interrupt active queries or transactions. Both approaches are described as temporary, as the underlying leakage will reappear after further activity.

Microsoft’s Response and Timeline

Microsoft confirmed the issue in a Wednesday update to the Windows release health dashboard. The company said it would release an out-of-band update within the next few days to address the bug. Until then, IT teams can contact Microsoft Support for Business to obtain a mitigation plan. The same support channel was also referenced for a separate memory-management workaround that had caused SQL Server crashes on Windows Server 2025 earlier in September.

What This Means for Web Hosting and Cloud Operators

For hosting providers and cloud operators that run SQL Server workloads on Windows, the leak poses a risk to uptime and performance. The accumulation of orphaned connections can lead to resource exhaustion, especially in high-traffic environments. Operators should monitor the number of open connections and consider implementing scripts that close idle links or schedule periodic SQL service restarts during low-usage windows. Additionally, reviewing the use of OLE DB providers for external data sources may help mitigate the impact until the patch is applied.

Next Steps for Administrators

1. Verify that your environment is running a version affected by the bug.
2. Use SQL Server management tools to list open linked server connections and close those that are idle.
3. Schedule a controlled restart of the SQL service during maintenance windows if performance degrades.
4. Contact Microsoft Support for Business for a tailored mitigation plan.
5. Apply the forthcoming out-of-band update as soon as it becomes available.

By following these steps, administrators can keep their SQL Server deployments stable while Microsoft delivers a permanent fix.