KB5087051: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 25H2 and Windows Server 2025, May 2026. Two framework flaws could let someone gain higher access

The update fixes two .NET Framework flaws that could let someone gain higher access. It installs through Windows Update and needs a restart if affected files are in use.

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

What changes

Fixes 2 changes

.NET Framework

2 items

A flaw that could let someone gain higher access is addressed.¹
Addresses CVE-2026-32177, an elevation-of-privilege vulnerability.
A flaw that could let someone gain higher access is addressed.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: KB5082417, KB5074828, KB5067931, KB5066128

+8 earlier
KB5066131, KB5066613, KB5064401, KB5056579, KB5054979, KB5049622, KB5045934, KB5044030
Replaced by: KB5100998

Version	File version	Channel
3.5	2.0.50727.9181	General availability
4.8.1	4.8.9335.0	General availability

Security

2 vulnerabilities fixed

2 important

Vulnerability	Severity	CVSS
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 2025 / Windows 11, version 25H2

91.8 MB

windows11.0-kb5087051-x64-ndp481.msu Main update · KB5087051 SHA-1: 1b5e85a2…4662d9

Arm64 Windows Server 2025 / Windows 11, version 25H2

109.9 MB

windows11.0-kb5087051-arm64-ndp481.msu Main update · KB5087051 SHA-1: e38715d2…d15fcd

Updated components

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

Top changed components	Files
WPF	28

Sources

Microsoft Support: KB5087051

Updated Oct 26, 2026

Cited passages from Microsoft's official notes (2)

1. This security update addresses a Elevation of Privilege vulnerability detailed in CVE-2026-32177. support.microsoft.com
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 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