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

KB5127689

KB5127689: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 10 21H2/22H2, October 2026. AD FS spoofing flaw and disclosed security bypass addressed

In short

Addresses 21 vulnerabilities. One is a critical AD FS spoofing flaw; another is a publicly disclosed .NET Framework security bypass.

Does it affect you? Applies to: Devices running Windows 10 version 21H2 or 22H2 with .NET Framework 3.5 or 4.8.1 installed.

File version
2.0.50727.9188 · 4.8.9363.0
Security
21 fixed · 1 critical
Restart
Required

What changes

Fixes 19 changes

.NET Framework

19 items
  • A denial-of-service flaw is addressed.1
    CVE-2026-58280: .NET Framework denial-of-service vulnerability.
  • An elevation-of-privilege flaw is addressed.2
    CVE-2026-69439: .NET Framework elevation-of-privilege vulnerability.
  • A denial-of-service flaw is addressed.3
    CVE-2026-69651: .NET Framework denial-of-service vulnerability.
  • A remote-code-execution flaw is addressed.4
    CVE-2026-70007: .NET Framework remote-code-execution vulnerability.
  • A remote-code-execution flaw is addressed.5
    CVE-2026-70035: .NET Framework remote-code-execution vulnerability.
  • A remote-code-execution flaw is addressed.6
    CVE-2026-70174: .NET Framework remote-code-execution vulnerability.
  • A remote-code-execution flaw is addressed.7
    CVE-2026-83520: .NET Framework remote-code-execution vulnerability.
  • A denial-of-service flaw is addressed.8
    CVE-2026-84008: .NET Framework denial-of-service vulnerability.
  • An elevation-of-privilege flaw is addressed.9
    CVE-2026-85363: .NET Framework elevation-of-privilege vulnerability.
  • A remote-code-execution flaw is addressed.10
    CVE-2026-87697: .NET Framework remote-code-execution vulnerability.
  • A spoofing flaw is addressed.11
    CVE-2026-96222: .NET Framework spoofing vulnerability.
  • A remote-code-execution flaw is addressed.12
    CVE-2026-96224: .NET Framework remote-code-execution vulnerability.
  • A denial-of-service flaw is addressed.13
    CVE-2026-96233: .NET Framework denial-of-service vulnerability.
  • A denial-of-service flaw is addressed.14
    CVE-2026-96958: .NET Framework denial-of-service vulnerability.
  • A denial-of-service flaw is addressed.15
    CVE-2026-96959: .NET Framework denial-of-service vulnerability.
  • A denial-of-service flaw is addressed.16
    CVE-2026-96960: .NET Framework denial-of-service vulnerability.
  • An information-disclosure flaw is addressed.17
    CVE-2026-97788: .NET Framework information-disclosure vulnerability.
  • A tampering flaw is addressed.18
    CVE-2026-97801: .NET Framework tampering vulnerability.
  • A security-feature bypass flaw is addressed.19
    CVE-2026-108398: .NET Framework security feature bypass vulnerability.

Technical details

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

Data sheet

Released
2026-10-13
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5126421, KB5120709
VersionFile versionChannel
3.5 2.0.50727.9188 General availability
4.8.1 4.8.9363.0 General availability

Security

21 vulnerabilities fixed
1 critical 18 important 2 not rated
VulnerabilitySeverityCVSS
CVE-2026-96222
Active Directory Federation Services (AD FS) Spoofing Vulnerability
 Critical 7.4
CVE-2026-102869
.NET and Visual Studio Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-108398
.NET Framework Security Feature Bypass Vulnerability
 Important 8.8
CVE-2026-70007
.NET Framework Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-70035
.NET Framework Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-70174
.NET Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-83520
.NET Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-85363
.NET Framework Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-96224
.NET Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-62886
.NET Elevation of Privilege Vulnerability
 Important 7.8
CVE-2026-58280
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-69651
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-84008
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-96233
ASP.NET Core Denial of Service Vulnerability
 Important 7.5
CVE-2026-96958
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-96959
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-96960
.NET Denial of Service Vulnerability
 Important 7.5
CVE-2026-97788
Active Directory Federation Services (AD FS) Information Disclosure Vulnerability
 Important 7.5
CVE-2026-97801
.NET Framework Tampering Vulnerability
 Important 7.5
CVE-2026-69439
.NET and Visual Studio Elevation of Privilege Vulnerability
 Not rated —
CVE-2026-87697
.NET Remote Code Execution Vulnerability
 Not rated —

Downloads (Microsoft Update Catalog)

x64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
92.9 MB
windows10.0-kb5127689-x64-ndp481.msu Main update · KB5127689 SHA-1: 36c0c67f…3d30d0
x86 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
61.8 MB
windows10.0-kb5127689-x86-ndp481.msu Main update · KB5127689 SHA-1: 87df8870…c3e6c7

Updated components

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

Top changed componentsFiles
ASP.NET54
WPF54
WCF44
.NET networking28
.NET data access22
.NET runtime (CLR)22
Windows Forms8

Sources

Updated
Cited passages from Microsoft's official notes (19)
  1. 1. This security update addresses a denial of service vulnerability detailed in CVE-2026-58280. support.microsoft.com
  2. 2. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-69439. support.microsoft.com
  3. 3. This security update addresses a denial of service vulnerability detailed in CVE-2026-69651. support.microsoft.com
  4. 4. This security update addresses a remote code execution vulnerability detailed in CVE-2026-70007. support.microsoft.com
  5. 5. This security update addresses a remote code execution vulnerability detailed in CVE-2026-70035. support.microsoft.com
  6. 6. This security update addresses a remote code execution vulnerability detailed in CVE-2026-70174. support.microsoft.com
  7. 7. This security update addresses a remote code execution vulnerability detailed in CVE-2026-83520. support.microsoft.com
  8. 8. This security update addresses a denial of service vulnerability detailed in CVE-2026-84008. support.microsoft.com
  9. 9. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-85363. support.microsoft.com
  10. 10. This security update addresses a remote code execution vulnerability detailed in CVE-2026-87697. support.microsoft.com
  11. 11. This security update addresses a spoofing vulnerability detailed in CVE-2026-96222. support.microsoft.com
  12. 12. This security update addresses a remote code execution vulnerability detailed in CVE-2026-96224. support.microsoft.com
  13. 13. This security update addresses a denial of service vulnerability detailed in CVE-2026-96233. support.microsoft.com
  14. 14. This security update addresses a denial of service vulnerability detailed in CVE-2026-96958. support.microsoft.com
  15. 15. This security update addresses a denial of service vulnerability detailed in CVE-2026-96959. support.microsoft.com
  16. 16. This security update addresses a denial of service vulnerability detailed in CVE-2026-96960. support.microsoft.com
  17. 17. This security update addresses an information disclosure vulnerability detailed in CVE-2026-97788. support.microsoft.com
  18. 18. This security update addresses a tampering vulnerability detailed in CVE-2026-97801. support.microsoft.com
  19. 19. This security update addresses a security feature bypass vulnerability detailed in CVE-2026-108398. support.microsoft.com
Checked automatically: 7 of 8 checks passed, 19 quoted passages · compared with Microsoft's page on Nov 14, 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 3/5, 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