From f8b5f0903c41ad420585c4a410173708bc3cea0e Mon Sep 17 00:00:00 2001 From: Tara Overfield Date: Thu, 20 Aug 2026 12:47:15 -0700 Subject: [PATCH 1/4] Update 08-11-august-cumulative-update.md Add known issues --- .../2026/08-11-august-cumulative-update.md | 22 ++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md index 1f7f25c3b7023..4e0b131ed6c15 100644 --- a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md +++ b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md @@ -1,12 +1,13 @@ --- title: August 2026 cumulative update description: Learn about the improvements in the .NET Framework August 2026 cumulative update. -ms.date: 08/11/2026 +ms.date: 08/20/2026 ai-usage: ai-generated --- # .NET Framework August 2026 cumulative update _Released August 11, 2026_ +_Updated August 20, 2026 to include known issues_ ## Summary of what's new in this release @@ -43,9 +44,24 @@ This security update addresses a remote code execution vulnerability detailed in There are no new quality and reliability improvements in this release. -## Known issues in this release +## **Known issues in this update** -This release contains no known issues. +**Known Issues:** After installing the August 2026 .NET Framework cumulative update, some WPF applications may fail with a `System.IO.FileFormatException` when printing or generating PDF/XPS content that uses certain fonts, including Calibri. + +**Workaround:** Applications may mitigate the issue by enabling the `Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection` AppContext switch in the app config file, as shown below. + +```xml + + + + + +``` + +This switch disables security protections introduced in the August 2026 update and may increase exposure to the vulnerabilities addressed by that update. Microsoft recommends using this workaround only as a temporary measure and only when required to address this issue. + +**Status:** Investigating. ## Summary tables From 8aafcb28979d274be2eae61555d887f012e61da9 Mon Sep 17 00:00:00 2001 From: Tara Overfield Date: Thu, 20 Aug 2026 14:38:35 -0700 Subject: [PATCH 2/4] Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> --- .../release-notes/2026/08-11-august-cumulative-update.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md index 4e0b131ed6c15..e1bc959175e0a 100644 --- a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md +++ b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md @@ -44,7 +44,7 @@ This security update addresses a remote code execution vulnerability detailed in There are no new quality and reliability improvements in this release. -## **Known issues in this update** +## Known issues in this release **Known Issues:** After installing the August 2026 .NET Framework cumulative update, some WPF applications may fail with a `System.IO.FileFormatException` when printing or generating PDF/XPS content that uses certain fonts, including Calibri. From f51eca9ffda3bceff37bc08fb47c20c21773d03e Mon Sep 17 00:00:00 2001 From: Tara Overfield Date: Thu, 20 Aug 2026 14:38:47 -0700 Subject: [PATCH 3/4] Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> --- .../release-notes/2026/08-11-august-cumulative-update.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md index e1bc959175e0a..0729b980d694c 100644 --- a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md +++ b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md @@ -7,7 +7,7 @@ ai-usage: ai-generated # .NET Framework August 2026 cumulative update _Released August 11, 2026_ -_Updated August 20, 2026 to include known issues_ +_Updated August 20, 2026, to include known issues._ ## Summary of what's new in this release From 5d42b6ed2f7372c5893494807c03af077fbc0426 Mon Sep 17 00:00:00 2001 From: Tara Overfield Date: Thu, 20 Aug 2026 14:39:41 -0700 Subject: [PATCH 4/4] Potential fix for pull request finding Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> --- .../release-notes/2026/08-11-august-cumulative-update.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md index 0729b980d694c..49b01ba36b79f 100644 --- a/docs/framework/release-notes/2026/08-11-august-cumulative-update.md +++ b/docs/framework/release-notes/2026/08-11-august-cumulative-update.md @@ -46,9 +46,9 @@ There are no new quality and reliability improvements in this release. ## Known issues in this release -**Known Issues:** After installing the August 2026 .NET Framework cumulative update, some WPF applications may fail with a `System.IO.FileFormatException` when printing or generating PDF/XPS content that uses certain fonts, including Calibri. +**Known issue:** After installing the August 2026 .NET Framework cumulative update, some WPF applications might fail with a `System.IO.FileFormatException` when printing or generating PDF/XPS content that uses certain fonts, including Calibri. -**Workaround:** Applications may mitigate the issue by enabling the `Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection` AppContext switch in the app config file, as shown below. +**Workaround:** Applications can mitigate the issue by enabling the `Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection` AppContext switch in the app config file, as shown below. ```xml