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HomeNovember 2026 patch cycleWindows CUs leave SQL Server linked server connections open

Known issueEnterprise

Issue from: October 2026 Patch Tuesday: 1,413 fixes, one exploited zero-day, and an Exchange hangover

Windows CUs leave SQL Server linked server connections open

Part of November 2026 patch cycle

Vendor
Microsoft
Products
Windows Server 2025, Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows 11 23H2 to 26H1, Windows 10 1809 and LTSC 2019, and SQL Server linked servers over OLE DB
Published
Status
Open

Call: Known issue. Microsoft has confirmed that Windows updates from October 13 onward can leave SQL Server linked server connections open after the query is done. They pile up and the server slows down. Microsoft says an out-of-band fix is coming “in the next few days.” November’s updates don’t fix it, since they include October’s changes. If your SQL Servers use linked servers to Oracle, PostgreSQL or anything else over OLE DB, start watching connection counts. It’s a slow leak, not an outage, so we wouldn’t pull a month of security fixes over it.

What breaks: In Microsoft’s words, “connections created by SQL Server linked server queries might remain open after the queries complete.” Each new query adds more, and “this can slow or degrade server performance after prolonged run time.” It affects linked server queries that use OLE DB providers. Oracle and PostgreSQL are the ones Microsoft names. The tell is a climbing count of open connections to the external database while no linked server queries are running.

Who’s hit: SQL Server boxes with OLE DB linked servers, after the October 13 update or anything later. Microsoft lists Server 2025, 2022, 2019 (and 1809), 2016, 2012 R2 and 2012, plus Windows 11 23H2 through 26H1 and Windows 10 1809 / LTSC 2019. The October KBs it names include KB5126646 (Server 2025), KB5126655 (Server 2022), KB5126651 (Server 2019) and KB5126836 (Server 2012 R2). Microsoft opened the issue on November 11. We haven’t seen admin reports outside Microsoft’s own entry yet.

Workaround:

  • Microsoft has a mitigation for business customers, but you have to get it through Microsoft Support for business. If this is hurting a production server, open the case now rather than when the OOB slips.
  • For short-term relief, close the idle connections or restart the SQL Server service. Microsoft warns that both can interrupt running queries and transactions, and that the problem comes back.
  • Graph connections from each SQL host to its linked targets, so you see the climb before your users do. Plan a service restart in a maintenance window if the count keeps climbing.
  • Install the out-of-band update when it ships. We’ll update this post when it does.

Sources: Server 2022 release health, Server 2025 release health, Server 2019 release health, Server 2012 R2 release health, Windows 11 24H2 release health.

Sources

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