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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Optional preview
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KB5056578

KB5056578: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 10 21H2/22H2, July 2025. Addresses type-converter concurrency and runtime error dialogs

In short

The update addresses a .NET type-conversion concurrency issue and error dialogs triggered by .NET DLL loads under OS code integrity enforcement. If you installed it previously, the July release requires no action.

Does it affect you? Applies to: Devices running Windows 10, version 21H2 or 22H2, with .NET Framework 3.5 or 4.8.1 installed. This includes Windows 10 Enterprise LTSC 2021.

File version
2.0.50727.9179 · 4.8.9310.0
Restart
Required

What changes

Fixes 2 changes

.NET Libraries

For: devices using .NET Framework

  • Addresses a concurrency issue affecting .NET type conversion and property lookup.1
    Addresses an issue with concurrency in TypeDescriptor.GetProperties() and TypeDescriptor.GetConverter().

.NET Runtime

  • Addresses error dialogs that can appear when .NET Framework DLLs load under the operating system’s code integrity policy.1
    Addresses interactions between .NET Framework DLL loads and OS code integrity enforcement policy that trigger error reporting dialog boxes.

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2025-07-08
Classification
Updates
Type
Cumulative update
Restart
Required
Replaces
KB5054978
Replaced by
KB5064400
VersionFile versionChannel
3.5 2.0.50727.9179 General availability
4.8.1 4.8.9310.0 General availability

Security

No vulnerabilities are listed for this update.

Downloads (Microsoft Update Catalog)

x64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
75.6 MB
windows10.0-kb5056578-x64-ndp481.msu Main update · KB5056578 SHA-1: 069b71df…f9a030
x86 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
47.1 MB
windows10.0-kb5056578-x86-ndp481.msu Main update · KB5056578 SHA-1: b5fde291…255523

Updated components

28 files changed since the previous update for the same versions.

Top changed componentsFiles
.NET runtime (CLR)18

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. .NET Runtime | - Addresses an issue where interactions between .NET Framework DLL loads and OS code integrity enforcement policy trigger error reporting dialog boxes. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 1 quoted passage · compared with Microsoft's page on Oct 20, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: passed

A second AI read the text against the sources: correctness 4/5, clarity 4/5, completeness 5/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake