Microsoft confirmed that the August 2026 .NET Framework cumulative update is causing printing and PDF/XPS export failures in some WPF applications, with errors affecting certain fonts such as Calibri. A temporary AppContext switch workaround is available, but Microsoft warns it disables protections added by the update and should only be used until a permanent fix is released. #.NETFramework #WPF #Calibri #Windows10 #Windows11 #WindowsServer2025
Keypoints
- August 2026 .NET Framework updates are breaking printing and PDF/XPS export in some applications.
- The issue affects apps built with the Windows Presentation Foundation (WPF) framework.
- Failures may trigger a System.IO.FileFormatException when certain fonts, including Calibri, are used.
- The problem impacts Windows client and Windows Server versions from Server 2012 through Server 2025.
- Microsoft provided a temporary workaround, but it disables protections added by the security update.