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

KB5087059

KB5087059: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows Server 2022, May 2026. Two flaws could give attackers more access

In short

Addresses two important security flaws in .NET Framework. It applies to Windows Server 2022 devices with .NET Framework 3.5 or 4.8.1 installed.

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 · 4.8.9334.0
Security
2 fixed
Restart
Required
Review notes Additional details from the official release notes (2) Read notes
  • What changes This item addresses a .NET Framework elevation-of-privilege security vulnerability.
  • What changes This item addresses a .NET Framework elevation-of-privilege security vulnerability.

The official sources are linked at the end of the page.

What changes

Improvements 2 changes

.NET Framework

2 items

For: Windows Server 2022 devices with .NET Framework 3.5 or 4.8.1

  • Addresses a security flaw that could let an attacker gain more access.1
    Addresses CVE-2026-32177, an Elevation of Privilege vulnerability.
  • Addresses a security flaw that could let an attacker gain more access.2
    Addresses CVE-2026-35433, an Elevation of Privilege vulnerability.

Technical details

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

Data sheet

Released
2026-05-12
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5082425, KB5066134
Replaced by
KB5101005
VersionFile versionChannel
3.5 2.0.50727.9181 General availability
4.8.1 4.8.9334.0 General availability

Security

2 vulnerabilities fixed
2 important
VulnerabilitySeverityCVSS
CVE-2026-32177
.NET Elevation of Privilege Vulnerability
 Important 7.3
CVE-2026-35433
.NET Elevation of Privilege Vulnerability
 Important 7.3

Downloads (Microsoft Update Catalog)

x64 Windows Server 2022
74.5 MB
windows10.0-kb5087059-x64-ndp481.msu Main update · KB5087059 SHA-1: 429d8898…ada069

Updated components

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

Top changed componentsFiles
WPF28

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. CVE-2026-32177 - .NET Framework Elevation of Privilege vulnerability support.microsoft.com
  2. 2. CVE-2026-35433 - .NET Framework Elevation of Privilege vulnerability support.microsoft.com
Checked automatically: 8 of 8 checks passed, 2 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: passed

A second AI read the text against the sources: correctness 3/5, 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