Microsoft: August updates break printing, PDF export in WPF apps
Microsoft August 2026 .NET Framework updates break printing and PDF export in WPF apps.
Microsoft has confirmed that its August 2026 .NET Framework cumulative updates are causing printing and PDF export failures in Windows Presentation Foundation (WPF) applications. The issue, which affects various Windows client and server versions, occurs when generating content with specific fonts like Calibri. Microsoft has provided a temporary workaround involving an AppContext switch, but warns this may disable security protections.
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The lesson from this incident
Full lessonMicrosoft's August 2026 cumulative .NET Framework update introduced a regression that breaks printing and PDF export in WPF applications when specific fonts such as Calibri are used. This highlights the persistent tension between applying security patches promptly and ensuring application stability in production environments. The offered workaround — an AppContext switch — explicitly disables security protections, forcing organizations into a difficult choice between operational continuity and security posture. This situation underscores why organizations must have structured patch testing pipelines and rollback capabilities before deploying cumulative updates broadly. Without these controls, a single faulty update can cause widespread business disruption across both client and server environments.
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