KB5122385: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 24H2/25H2, August 2026. Intermittent crashes addressed in 64-bit .NET scenarios

Addresses intermittent crashes in some 64-bit .NET Framework scenarios.

Does it affect you? Applies to: Windows 11, versions 24H2 and 25H2, and Microsoft server operating system 24H2 devices with .NET Framework 3.5 or 4.8.1 installed.

What changes

Improvement 1 change

.NET Fundamentals

Intermittent crashes might occur less often in some 64-bit .NET Framework scenarios.¹
Addresses intermittent crashes in some 64-bit .NET Framework scenarios.

Technical details

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

Data sheet

Released: 2026-08-27
Classification: Updates
Type: Cumulative update
Restart: Required
Replaces: KB5092427, KB5092430, KB5074828, KB5074831

+8 earlier
KB5067931, KB5066613, KB5064401, KB5056579, KB5054979, KB5050577, KB5048162, KB5045934
Replaced by: KB5126052

Version	File version	Channel
3.5	2.0.50727.9183	General availability
4.8.1	4.8.9345.0	General availability

Security

No vulnerabilities are listed for this update.

Downloads (Microsoft Update Catalog)

x64 Windows 11, version 24H2 / Windows 11, version 25H2

92.3 MB

windows11.0-kb5122385-x64-ndp481.msu Main update · KB5122385 SHA-1: c3cddfc7…446749

Arm64 Windows 11, version 24H2 / Windows 11, version 25H2

110.6 MB

windows11.0-kb5122385-arm64-ndp481.msu Main update · KB5122385 SHA-1: f11a8009…0b5f7d

Updated components

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

Top changed components	Files
ASP.NET	22
WPF	18
WCF	12
.NET networking	11
.NET runtime (CLR)	11
.NET data access	7
Windows Forms	2

Sources

Updated Oct 26, 2026

Cited passages from Microsoft's official notes (1)

1. Addresses an issue where intermittent crashes could occur in some 64-bit .NET Framework scenarios. 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 5/5, clarity 5/5, 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