Microsoft has confirmed a known issue causing Microsoft Teams and the new Outlook for Windows to crash or fail to launch on ARM-based PCs after installing security updates released on or after August 11, 2026.

The problem traces back to the KB5121003 update, part of Microsoft’s August 2026 Patch Tuesday rollout, and specifically affects devices running on Windows-on-ARM silicon, such as the Surface Pro 11 and Surface Laptop 7.

According to an advisory Microsoft posted to the Windows release health dashboard on September 1, 2026, at 19:20 PT, affected users may find that Teams and the new Outlook either refuse to open at all or close unexpectedly shortly after launching.

Notably, classic Outlook, Word, Excel, and other Microsoft 365 applications remain unaffected, suggesting the fault lies within the packaged app model used by modern Store-delivered apps rather than the underlying Office suite itself.

Microsoft Teams, Outlook Fail Crash

Microsoft says the issue is most likely to surface on new or freshly imaged PCs that have not yet received recent Microsoft Store updates, pointing to a dependency conflict introduced by the security patch rather than a fundamental flaw in the apps themselves.

Community reports on Microsoft’s Q&A forums and Tech Community boards had flagged the crashes as early as mid-August, with logs pointing to AppX and MSIX packaging errors, including the error code 0x80073CFC during token generation for the Outlook package.

The affected platforms include Windows 11 version 24H2, 25H2, and the newer 26H1 release, which requires specific Arm-based silicon such as Qualcomm’s Snapdragon X2 chips. No server platforms are impacted by this issue.

While Microsoft has not disclosed the technical root cause, the company has published a temporary workaround rather than a full fix. Affected users are advised to open the Microsoft Store, navigate to Downloads, select Check for updates, and install the latest version of the Auto Super Resolution Package, specifically version 1.0.19.0 or later.

This package is typically designed to help Copilot+ PCs use AI-driven upscaling for smoother gameplay, making its connection to Outlook and Teams stability somewhat unexpected.

Microsoft has marked the issue’s status as “Mitigated” on its release health dashboard, indicating that the workaround addresses the immediate disruption while a permanent fix is still in development. The company has stated it is working to resolve the problem through a future Windows update and will share additional details once available.

For enterprise IT administrators managing fleets of Arm-based Windows devices, this incident is a reminder to verify Microsoft Store updates before deploying new security patches, particularly on freshly provisioned hardware where the packaged app dependencies have not yet synchronized.

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