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.NET Framework 4.8.1 · Release Health

Known issues in .NET Framework 4.8.1

Problems Microsoft has confirmed for this version, from its official release health notes. 1 still open or mitigated.

.NET Framework: 4.8.1 4.8 4.7.2 3.5
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Active known issues

Open & Mitigated
1 active issue
  1. Open .NET Framework 3.5 4.8.1 Affects: Organizations and IT administrators Started with KB5056580 · Jul 8, 2025

    The Windows 11, version 22H2 package KB5056580 was not available on Windows Server Update Services (WSUS) or Microsoft Update Catalog

    The Windows 11, version 22H2 package was missing from WSUS and the Update Catalog. Microsoft published it there on July 14, 2025.

    How to apply the workaround Workaround

    Before it was published there, the package could be installed through Windows Update or Microsoft Update.

Recently resolved

Fixed in latest updates
3 resolved
  1. Resolved .NET Framework 3.5 4.7.2 4.8 4.8.1 Affects: Everyone Started with KB5120698 · Aug 11, 2026

    After installing the August 2026 .NET Framework cumulative update, WPF applications that print—or display print preview…

    After the August 2026 update, WPF applications might fail to print or show print preview for some in-memory XPS documents registered with System.IO.Packaging.PackageStore. The issue is resolved in the October 2026 .NET Framework cumulative update and later updates.

    How to apply the workaround Workaround

    Rebuild affected applications with an absolute package identity that does not use the pack scheme. If an application cannot be rebuilt, temporarily enable the AppContext switch; Microsoft warns that it disables security protections and may increase exposure to the vulnerabilities addressed by the update.

    Step-by-step workaround instructions
    2 steps
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    Step-by-step procedure
    1. For applications that can be rebuilt, use an absolute package identity such as xpspack://<guid>.xps instead of a pack scheme identity.
    2. For applications that cannot be rebuilt, add Switch.System.Windows.DisableXpsPackageBoundaryRestriction=true to AppContextSwitchOverrides in the application config file.
  2. Resolved .NET Framework 3.5 4.7.2 4.8 4.8.1 Affects: Everyone Started with KB5120698 · Aug 11, 2026

    After installing the August 2026 .NET Framework cumulative update, some WPF applications may fail with a System.IO.File…

    After the August 2026 update, some WPF applications might fail with a System.IO.FileFormatException when printing or generating PDF/XPS content that uses certain fonts, including Calibri. The issue is resolved in the September 2026 .NET Framework cumulative update and later updates.

    How to apply the workaround Workaround

    Temporarily enable the AppContext switch in the application config file; Microsoft warns this disables security protections and may increase exposure to the vulnerabilities addressed by the update.

  3. Resolved .NET Framework 3.5 4.8 4.8.1 Affects: Organizations and IT administrators Started with KB5037926 · May 14, 2024 Fixed by KB5043804

    Microsoft received reports about .NET Framework May cumulative update causing customers to observe runtime exceptions in certain SQL CLR hosted scenarios

    Some SQL CLR apps might get runtime exceptions when using SHA256Managed, SHA384Managed, or SHA512Managed. The issue is resolved by KB5043806; SHA1Managed, HMACSHA1, HMACSHA256, HMACSHA284, and HMACSHA512 are not affected.

    How to apply the workaround Workaround

    Mark the assembly that uses one of the affected hash types as UNSAFE, or use SQL Server's HASHBYTES function instead of the .NET Framework SHA-2 APIs.

    Step-by-step workaround instructions
    2 steps
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    Step-by-step procedure
    1. For an assembly that uses SHA256Managed, SHA384Managed, or SHA512Managed, mark it as [UNSAFE].
    2. Alternatively, use SQL Server's HASHBYTES function instead of the .NET Framework SHA-2 APIs.

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