--- title: Microsoft: August updates break printing, PDF export in... description: Microsoft has confirmed that the August 2026 .NET Framework cumulative update breaks printing and PDF/XPS export in WPF applications, causing a... canonical: https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Microsoft: August updates break printing, PDF export in WPF apps | daily.dev og:description: Microsoft has confirmed that the August 2026 .NET Framework cumulative update breaks printing and PDF/XPS export in WPF applications, causing a... og:url: https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn og:image: https://api.daily.dev/og/posts/MTBUVQlMN.png og:image:alt: Microsoft: August updates break printing, PDF export in WPF apps og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Microsoft: August updates break printing, PDF export in WPF apps **[BleepingComputer](https://daily.dev/sources/bleepingcomputer)** · 2 min read · 0 upvotes · 0 comments ## Summary Microsoft has confirmed that the August 2026 .NET Framework cumulative update breaks printing and PDF/XPS export in WPF applications, causing a System.IO.FileFormatException when certain fonts like Calibri are used. The issue affects Windows 10, Windows 11, and Windows Server versions from 2012 through 2025. Microsoft is still investigating a permanent fix but offers a temporary workaround via an AppContext switch that disables Cmap and Sbit overflow protection - though this also removes security protections shipped in the same update, exposing systems to vulnerabilities the update was meant to patch. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why do my WPF apps throw a System.IO.FileFormatException when printing or exporting to PDF after installing the August 2026 .NET Framework update? The August 2026 .NET Framework cumulative update introduced a bug that breaks printing and PDF/XPS generation in WPF applications when certain fonts, including Calibri, are used, causing a System.IO.FileFormatException. Microsoft confirmed this affects Windows 10, Windows 11, and Windows Server 2012 through 2025, and is still investigating a permanent fix. _Track known .NET Framework issues like this WPF printing bug as fixes roll out on daily.dev._ ### What is the workaround for the WPF printing and PDF export bug caused by the August 2026 .NET Framework update? Enable the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch in the application config file under the runtime section. This resolves the printing and PDF/XPS export failures, but Microsoft warns it also disables security protections shipped in the same update, so it should only be used temporarily until an official fix ships. _daily.dev helps developers weigh temporary workarounds like this against the security trade-offs involved._ ## Similar posts on daily.dev - [Latest Windows 11 updates may break the OS's most basic bits](https://daily.dev/posts/latest-windows-11-updates-may-break-the-os-s-most-basic-bits-xwpxl3qea) · The Register · 0 upvotes · 0 comments - [Microsoft broke some OLE automations with latest Windows update](https://daily.dev/posts/microsoft-broke-some-ole-automations-with-latest-windows-update-5r2mcea8e) · CSO Online · 0 upvotes · 0 comments - [Every month Windows gets an emergency patch, and I'm running out of reasons to stay](https://daily.dev/posts/every-month-windows-gets-an-emergency-patch-and-i-m-running-out-of-reasons-to-stay-3knfifu3f) · XDA Developers · 0 upvotes · 0 comments - [Microsoft confirms Office apps launch issues after June updates](https://daily.dev/posts/microsoft-confirms-office-apps-launch-issues-after-june-updates-ru1hrq2qo) · BleepingComputer · 1 upvotes · 0 comments --- Tags: [#windows](https://daily.dev/tags/windows), [#.net](https://daily.dev/tags/.net), [#wpf](https://daily.dev/tags/wpf) [View this post on daily.dev](https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Microsoft: August updates break printing, PDF export in WPF apps","url":"https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn"},"datePublished":"2026-08-24T12:40:32.970Z","dateModified":"2026-08-24T12:40:53.981Z","description":"Microsoft has confirmed that the August 2026 .NET Framework cumulative update breaks printing and PDF/XPS export in WPF applications, causing a...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/018382ca42eaf915e9a5bc3abef96ace?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/018382ca42eaf915e9a5bc3abef96ace?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"BleepingComputer","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"BleepingComputer","logo":"https://media.daily.dev/image/upload/s--as8nJ3qy--/f_auto,q_auto/v1774959951/logos/bleepingcomputer?_a=BAMAMiWQ0","url":"https://daily.dev/sources/bleepingcomputer"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"windows,.net,wpf","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"BleepingComputer","item":"https://daily.dev/sources/bleepingcomputer"},{"@type":"ListItem","position":3,"name":"Microsoft: August updates break printing, PDF export in WPF apps"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps-mtbuvqlmn#faq","mainEntity":[{"@type":"Question","name":"Why do my WPF apps throw a System.IO.FileFormatException when printing or exporting to PDF after installing the August 2026 .NET Framework update?","acceptedAnswer":{"@type":"Answer","text":"The August 2026 .NET Framework cumulative update introduced a bug that breaks printing and PDF/XPS generation in WPF applications when certain fonts, including Calibri, are used, causing a System.IO.FileFormatException. 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