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August updates break printing, PDF export in WPF apps
Microsoft has acknowledged that recent updates to the .NET Framework from August 2026 are hindering printing and PDF generation in certain WPF applications. Users experience System.IO.FileFormatException errors due to specific fonts, such as Calibri. This issue impacts various Windows client and server releases. Microsoft has proposed a temporary fix, although it could compromise system protections against vulnerabilities addressed in the updates.
MonitorConfidence: HighShort term horizon
Published 24 Aug 2026, 12:50 UTC1 min read
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Summary
TL;DR
- August 2026 updates disrupt printing in WPF applications
- System.IO.FileFormatException occurs when generating PDFs
- Impact affects multiple Windows client and server versions
- Temporary workaround exposes system to security risks
- Microsoft continues to investigate the known issue
Interesting facts
- This isn't the first time WPF apps have faced issues after updates, similar problems were noted in February 2021.
- The workaround disables critical security protections that were part of the August update.
Coverage gaps