KB5131291: Windows Server 2016 Security Update (November 2026)

1. Users might be unable to sign in to OWA or send emails on Exchange Server

Symptoms:

After installing this update, some on-premises Exchange servers might experience issues accessing or sending email. Users might be unable to sign in to Outlook on the web (OWA), or email messages sent from Outlook might remain in the Outbox and not be delivered. Additionally, Exchange might experience issues accessing mailboxes during mailbox replication.

In some affected configurations, Exchange Server OWA might fail with an error MapiExceptionMdbOffline: Unable to make connection to the server. (hr=0x80004005, ec=1142) with Event ID 1006 logged in the application log. Another reported symptom is growing email queues. Installing the October 2026 Exchange server security updates isn’t required for these issues to occur.

Resolution

This issue is resolved in Windows updates released on and after November 10, 2026 such as (KB5131291) . We recommend you install the latest Windows update for your device as it contains important improvements and issue resolutions, including this one.

2. USB Audio Class 1.0 devices with error Code 10 or no output

Symptoms

After installing the September 8, 2026, Windows security update, some USB Audio Class 1.0 devices might fail to start or produce audio. Affected devices might experience one or more of the following symptoms:

The device displays an error in Device Manager: "This device cannot start (Code 10).”

No audio output.

Volume controls are unresponsive or remain at zero.

Sound settings are unresponsive or unavailable.

Some devices might function in standard stereo configurations but fail when using multichannel audio features, including 8-channel or 3D audio modes. Some customers have reported that they're able to restore audio in these cases by switching to 2-channel mode.

This issue is limited to USB Audio Class 1.0 devices.

Resolution

The symptoms experienced on devices using 8-channel or 3D audio modes are addressed in the out-of-band (OOB) update released on September 14, 2026, (KB5129239) . The remaining symptoms are addressed in (KB5131291) .