Microsoft breaks WPF printing with .NET update
- ID
- 17649
- Status
- summarized
- Published
- 25 Aug 2026, 7:27 PM
- Fetched
- 25 Aug 2026, 10:42 PM
- Provider
- The Register
- Category
- technology
- Original URL
- https://www.theregister.com/os-platforms/2026/08/25/microsoft-breaks-wpf-printing-with-net-update/5292116
- Source URL
- https://www.theregister.com/headlines.atom
Summary
- Score
- 6.5
- Created
- 25 Aug 2026, 10:44 PM
- Tags
- Audience
- developers
What happened
Microsoft's August 11, 2026 .NET Framework cumulative update broke WPF printing and PDF/XPS generation, causing a System.IO.FileFormatException when content uses certain fonts including Calibri. The bug affects Windows 10, 11, and Windows Server 2012 through 2025. Microsoft's workaround—enabling Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection in app config—disables security protections introduced in the same update, forcing a tradeoff between printing functionality and security.
Why it matters
If you ship or maintain WPF applications that print or export PDF/XPS, test immediately against the August 2026 .NET Framework update. You must decide whether to apply the workaround (which re-opens vulnerabilities the update was meant to fix) or hold off on the update entirely until Microsoft patches it. .NET/WPF remains common in Malaysian enterprise and government line-of-business apps, so this is likely to surface in production environments soon.
Discussion angle
The security-vs-functionality tradeoff is the real story: Microsoft shipped a security fix that breaks a core WPF capability, and the only workaround re-exposes the very vulnerabilities the update addresses. Discuss how teams should handle this in environments where printing is business-critical and skipping security updates isn't acceptable.