Microsoft: August updates break printing, PDF export in WPF apps
Microsoft has confirmed that .NET Framework updates released as part of the August 2026 Patch Tuesday are breaking printing and PDF export in some applications. The issue affects only apps that use the Windows Presentation Foundation (WPF) UI framework.
Intelligence analysis by Llama
Microsoft has confirmed that .NET Framework updates released in August 2026 are breaking printing and PDF export in some WPF applications. A temporary fix is available, but it disables protections introduced with the August 2026 .NET Framework update.
Imagine you're trying to print a document, but the printer is having trouble reading the font. That's what's happening with some Windows applications that use a special kind of software called WPF. Microsoft is working on a fix, but in the meantime, users can try a temporary workaround that disables some security features.
Analysis
Affected Platforms and Applications
Microsoft has confirmed that the issue affects both Windows client releases (including the latest versions of Windows 10 and Windows 11) and Windows Server (from Windows Server 2012 up to Windows Server 2025). The problem specifically affects applications that use the Windows Presentation Foundation (WPF) UI framework, an open-source graphical subsystem for building Windows desktop client applications.
Temporary Fix and Risks
Microsoft has provided a temporary fix to help affected users work around these printing problems. However, this workaround requires enabling the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch in the application config file. This will also disable protections introduced with the August 2026 .NET Framework update, exposing the system to attacks that could exploit vulnerabilities addressed by this month's security updates.
Investigation and Permanent Solution
Microsoft is still investigating the issue and has not yet shipped a permanent solution. In the meantime, users are advised to use the temporary fix only as a last resort and only when required to address this issue.
Key points
- Microsoft has confirmed that .NET Framework updates released in August 2026 are breaking printing and PDF export in some WPF applications.
- The issue affects both Windows client releases and Windows Server.
- A temporary fix is available, but it disables protections introduced with the August 2026 .NET Framework update.
- Microsoft is still investigating the issue and has not yet shipped a permanent solution.
Microsoft is actively investigating the issue and has provided a temporary fix to help affected users. A permanent solution is expected to be released soon, which will resolve the printing and PDF export issues.
The temporary fix provided by Microsoft disables some security features, which may leave users vulnerable to attacks that could exploit vulnerabilities addressed by this month's security updates.
