Microsoft Teams, Outlook Crash on ARM Devices After August 2026 Updates
Microsoft Teams and the new Outlook for Windows are crashing on ARM-based devices following the August 2026 security updates, specifically KB5121003.
Microsoft has confirmed a widespread issue impacting Microsoft Teams and the new Outlook for Windows, causing them to crash or fail to launch on ARM-based PCs. The problem emerged after the installation of security updates released on or after August 11, 2026, with the specific culprit identified as the KB5121003 update, part of Microsoft's August 2026 Patch Tuesday rollout.
This bug primarily affects devices running on Windows-on-ARM silicon, such as the Surface Pro 11 and Surface Laptop 7, and is particularly noticeable on new or freshly imaged PCs that have not yet received recent Microsoft Store updates. Affected users report that Teams and the new Outlook either refuse to open at all or close unexpectedly shortly after launching. Notably, classic Outlook and other Microsoft 365 applications like Word and Excel remain unaffected, suggesting the issue is tied to the modern Store-delivered app packaging rather than the core Office suite.
Community reports began flagging these crashes in mid-August, with system logs pointing towards AppX and MSIX packaging errors, including specific error codes like 0x80073CFC during token generation for the Outlook package. The affected Windows versions are Windows 11 versions 24H2, 25H2, and the newer 26H1 release, all of which require specific Arm-based silicon, such as Qualcomm's Snapdragon X2 chips. Microsoft has clarified that no server platforms are impacted by this particular issue.
While the precise technical root cause has not been publicly disclosed by Microsoft, the company has provided a temporary workaround to mitigate the disruption. Users experiencing these crashes are advised to open the Microsoft Store, navigate to the 'Downloads' section, select 'Check for updates,' and install the latest version of the Auto Super Resolution Package. This package, typically designed for AI-driven upscaling on Copilot+ PCs, is now being used to address the stability problems in Teams and Outlook.
Microsoft has marked the issue's status as "Mitigated" on its Windows release health dashboard, indicating that the provided workaround effectively addresses the immediate user impact. However, a permanent fix is still under development, and Microsoft has committed to releasing it through a future Windows update, promising to share more details once they become available.
For IT administrators managing fleets of ARM-based Windows devices, this incident serves as a crucial reminder to carefully vet Microsoft Store updates before deploying new security patches, especially on newly provisioned hardware where application dependencies might not yet be fully synchronized. The unexpected link between a graphics-related package and application stability highlights the complex interdependencies within modern operating systems and application delivery mechanisms.
The affected platforms include Windows 11 version 24H2, 25H2, and 26H1, specifically on devices utilizing Arm-based processors like Qualcomm's Snapdragon X2 chips. This targeted impact underscores the unique challenges and potential vulnerabilities associated with the Windows-on-ARM ecosystem.
This situation underscores the importance of robust testing and validation processes for both OS updates and application delivery systems, particularly as Microsoft continues to integrate AI features and refine its app packaging technologies.