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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Security update
Patch Tuesday

KB5087055

KB5087055: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 26H1, May 2026. Two framework flaws could allow higher access

In short

Addresses two .NET Framework flaws that could let someone gain higher access: CVE-2026-32177 and CVE-2026-35433.

Does it affect you? Applies to: Devices running Windows 11, version 26H1, with .NET Framework 4.8.1 installed. The update covers .NET Framework 3.5 and 4.8.1.

File version
4.8.9335.0
Security
2 fixed
Restart
Required

What changes

Fixes 2 changes

.NET Framework

2 items
  • A flaw could let someone gain higher access.1
    CVE-2026-32177 is an elevation-of-privilege vulnerability.
  • A flaw could let someone gain higher access.2
    CVE-2026-35433 is 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
KB5082421, KB5074837
Replaced by
KB5101002
VersionFile versionChannel
3.5 General availability
4.8.1 4.8.9335.0 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)

Arm64 Windows 11, version 26H1
55.0 MB
windows11.0-kb5087055-arm64-ndp481.msu Main update · KB5087055 SHA-1: 0e747a56…6931d2

Updated components

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

Top changed componentsFiles
WPF33

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. This security update addresses a Elevation of Privilege vulnerability detailed in CVE-2026-32177. support.microsoft.com
  2. 2. This security update addresses a Elevation of Privilege vulnerability detailed in CVE-2026-35433. support.microsoft.com
Checked automatically: 7 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: not passed

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