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Microsoft Teams and Outlook might fail to launch on ARM-based devices

Microsoft lists this known issue for 3 Windows versions; its status is Resolved. It started with KB5121000, KB5121003. Microsoft resolved it in KB5124008, KB5124012.

Resolved1 version

Facts

Microsoft id
4959
Status
Resolved
Products
Windows 11, version 24H2, Windows 11, version 25H2, Windows 11, version 26H1
Versions
Windows 11, version 24H2, Windows 11, version 25H2, Windows 11, version 26H1
Originating KBs
KB5121000, KB5121003
Resolved by
KB5124008, KB5124012
First captured by us
(from our first import of this list)
Microsoft last modified
Source
Windows known issues · open the original at Microsoft

Status per Windows version

VersionStatusOriginating updateOpenedResolved
Windows 11, version 26H1Resolved KB5124012OS Build 28000.2704, KB5121000, 2026-08-112026-09-02 01:46 UTC2026-09-08 17:00 UTC
Windows 11, version 25H2Resolved KB5124008OS Build 26200.9168, KB5121003, 2026-08-112026-09-02 01:46 UTC2026-09-08 17:00 UTC
Windows 11, version 24H2Resolved KB5124008OS Build 26100.9168, KB5121003, 2026-08-112026-09-02 01:46 UTC2026-09-08 17:00 UTC

Microsoft says

After installing Windows security updates released on or after August 11, 2026, (KB5121000), Microsoft Teams and the new Outlook for Windows might fail to launch…

Windows known issues,

Read Microsoft's full post

What Microsoft changed

One version so far. If Microsoft edits it, each change shows here with what was removed and added.

  1. First version we captured ·

    As first seen: Resolved
    Status
    Resolved

    Seen by us · Microsoft's timestamp · Microsoft's page

Mentioning the same Microsoft ids

Last updated