SQL Server linked server bug after October update leaks connections
Microsoft admits the October 13 update (KB5126646) can leave SQL Server linked server connections open, slowing servers until someone restarts the service.
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giftdetect· the right gift in minutesIf your SQL Server has been acting strangely since the October update, Microsoft now says it knows why. The update KB5126646, released on October 13, can leave linked server connections open when they should have been closed.
Linked servers let SQL Server pull data from other databases through OLE DB providers. In theory, the server opens a connection, grabs the data and closes it again when the query finishes. After the update, that last step doesn't always happen. According to Microsoft, "connections to external databases can accumulate instead of closing as expected," and that "can slow or degrade server performance after prolonged run time."
Microsoft names PostgreSQL and Oracle as examples of connections known to be affected. Administrators will probably have already spotted an odd number of open connections to external databases.
How do you fix the SQL Server linked server connection problem?
There is no real fix yet. If idle connections can be identified, you can close them by hand to ease the load for a while. Restarting the SQL service also restores stability temporarily. Microsoft itself warns that both steps can interrupt active queries or transactions, and the problem can come back after enough running time.
A mitigation exists, but only through Microsoft support for business customers. For everyone else, Microsoft says an out-of-band update (a fix released outside the normal Patch Tuesday schedule) should arrive within the next few days.
Which Windows versions are affected?
Almost all of them. Microsoft says the issue hits every version of Windows except Windows 11 26H2, going back to Windows 10 1809 and LTSC 2019. On the server side that means Windows Server from 2025 back to 2012.
It has been a rough stretch for people who run Microsoft server products. The October 2026 Windows Server update also left some Exchange Servers unstable until admins made a Registry edit or installed the fix included in the November update.
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