Windows Printing Is Broken After Microsoft’s August Updates

Microsoft has confirmed that .NET Framework updates released with the August 2026 Patch Tuesday are causing printing and PDF export problems in some Windows applications.

The issue affects apps built with Windows Presentation Foundation, or WPF. Microsoft says affected applications can fail with a System.IO.FileFormatException when printing or generating PDF/XPS content that uses certain fonts, including Calibri.

Windows 10, Windows 11, and Windows Server are affected

The problem affects current versions of Windows 10 and Windows 11, along with Windows Server versions from Windows Server 2012 through Windows Server 2025.

Microsoft says the issue only affects applications that rely on the impacted WPF functionality, so not every Windows app will encounter printing or PDF export failures.

Microsoft has a temporary workaround

Microsoft is still investigating the problem and has not released a permanent fix.

For now, administrators and developers can enable the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch inside the affected application’s configuration file.

The change allows affected WPF applications to resume printing and generating PDF/XPS documents.

The workaround lowers security protections

Microsoft warns that the workaround disables protections introduced by the August 2026 .NET Framework security updates.

That creates a tradeoff. Enabling the switch may restore printing, but it could also expose systems to attacks that target vulnerabilities addressed by the latest updates.

The warning is especially notable because August’s Patch Tuesday fixed more than 400 vulnerabilities.

Microsoft recommends using the workaround only when necessary and removing it once a permanent fix becomes available.

This is not the only problem linked to the August updates. Microsoft has also shared a temporary workaround for game crashes and freezes caused by KB5121003.

Via BleepingComputer