Microsoft said on November 11 that SQL Server linked server queries can leave connections to external databases open after the query finishes on systems that installed the October 2026 monthly security updates. The company said it will release an out-of-band update within days to address the problem.
The issue matters because the open connections can stack up each time a query runs. Over time, that buildup can slow affected servers, and in some cases the number of connections keeps rising even when no related queries are active.
Microsoft linked the problem to SQL Server connections made through OLE DB providers, with impact reported on Oracle and PostgreSQL. The company said the defect has been confirmed on systems that took the October 2026 monthly security updates, while Windows 11 version 26H2 is not listed among the affected systems as of the article’s writing.
The company said the problem is not resolved by a workaround alone. Administrators can identify idle connections and disconnect them manually, or restart the SQL service, but those steps only clear the buildup until the queries run again. Microsoft said mitigation measures are available for enterprise devices through enterprise support while the out-of-band update is pending.
This is the kind of fault that can sit unnoticed until a server has been running for a long stretch and then start to drag on performance. Microsoft’s own description points to a narrow but stubborn pattern: the queries complete, the connections do not close, and the count rises in the background. The emergency update due within days is the first real fix, and until it arrives, administrators are left managing the leak instead of sealing it.
