Skip to the content
The Update Bureau
.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Security update
Patch Tuesday

KB5082425

KB5082425: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows Server 2022, April 2026. Critical denial-of-service flaw addressed; ARM64 runtime crash improved

In short

The update addresses six vulnerabilities, including a critical .NET Framework denial-of-service flaw, and reliability issues in ClickOnce, the ARM64 runtime, and WCF.

Does it affect you? Applies to: Windows Server 2022 devices with .NET Framework 3.5 or 4.8.1 installed.

File version
2.0.50727.9181 · 4.8.9332.0
Security
6 fixed · 1 critical
Restart
Required

What changes

Fixes 3 changes

.NET Runtime

2 items
  • ClickOnce gains verification logic for SHA384 and SHA512.1
    Addresses an issue by adding ClickOnce verification logic to support SHA384 and SHA512.
  • Addresses an issue that could make the .NET runtime crash on ARM64 when code generates and catches a NullReferenceException in the same function.2
    Addresses an issue where the arm64 CLR could crash when code generates and catches a NullReferenceException within the same function.

WCF

Verified in package
  • Addresses an issue with WCF NamedPipe services running inside a Win32 app container on Windows 11 or Windows Server 2025.3
    Addresses an issue with running a WCF NamedPipe service inside a Win32 app container on Windows 11 or Windows Server 2025.

Technical details

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

Data sheet

Released
2026-04-14
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5066134, KB5065753
Replaced by
KB5087059
VersionFile versionChannel
3.5 2.0.50727.9181 General availability
4.8.1 4.8.9332.0 General availability

Security

6 vulnerabilities fixed
1 critical 2 important 3 not rated
VulnerabilitySeverityCVSS
CVE-2026-23666
.NET Framework Denial of Service Vulnerability
 Critical 7.5
CVE-2026-33116
.NET, .NET Framework, and Visual Studio Denial of Service Vulnerability
 Important 7.5
CVE-2026-32226
.NET Framework Denial of Service Vulnerability
 Important 5.9
CVE-2026-26171
.NET Denial of Service Vulnerability
 Not rated —
CVE-2026-32178
.NET Spoofing Vulnerability
 Not rated —
CVE-2026-32203
.NET and Visual Studio Denial of Service Vulnerability
 Not rated —

Downloads (Microsoft Update Catalog)

x64 Windows Server 2022
74.5 MB
windows10.0-kb5082425-x64-ndp481.msu Main update · KB5082425 SHA-1: 435f5397…e52bf0

Updated components

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

Top changed componentsFiles
WCF14
.NET runtime (CLR)12
Windows Forms2

Verified in package: changed files confirm WCF.

Sources

Updated
Cited passages from Microsoft's official notes (3)
  1. 1. Addresses an issue to add verification logic for ClickOnce to support SHA384 and SHA512 support.microsoft.com
  2. 2. Addresses an issue where arm64 CLR could crash when code generates and catches a NullReferenceException within the same function support.microsoft.com
  3. 3. Addresses an issue with running a WCF NamedPipe service inside a Win32 app container when running on Windows 11 or Windows Server 2025. support.microsoft.com
Checked automatically: 7 of 8 checks passed, 3 quoted passages · compared with Microsoft's page on Sep 25, 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: not 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