Skip to the content
The Update Bureau
.NET Framework 3.5 / 4.7.2 .NET Framework 3.5 / 4.7.2 Security update
Patch Tuesday

KB5127666

KB5127666: Cumulative update for .NET Framework, versions 3.5 and 4.7.2, on Windows 10 1809 and Windows Server 2019, October 2026. Publicly disclosed .NET security bypass addressed

In short

The update addresses 21 vulnerabilities, including one critical flaw. CVE-2026-108398 could bypass a .NET Framework security protection and was publicly disclosed.

Does it affect you? Applies to: Devices running Windows 10, version 1809, or Windows Server 2019 with .NET Framework 3.5 or 4.7.2 installed.

File version
2.0.50727.9073 · 4.7.4150.0
Security
21 fixed · 1 critical
Restart
Required

What changes

Fixes 19 changes

.NET Framework

19 items
  • The update addresses a flaw that could make a service unavailable.1
    CVE-2026-58280: denial-of-service vulnerability.
  • The update addresses a flaw that could let someone gain higher permissions.2
    CVE-2026-69439: elevation-of-privilege vulnerability.
  • The update addresses a flaw that could make a service unavailable.3
    CVE-2026-69651: denial-of-service vulnerability.
  • The update addresses a flaw that could let an attacker run code.4
    CVE-2026-70007: remote-code-execution vulnerability.
  • The update addresses a flaw that could let an attacker run code.5
    CVE-2026-70035: remote-code-execution vulnerability.
  • The update addresses a flaw that could let an attacker run code.6
    CVE-2026-70174: remote-code-execution vulnerability.
  • The update addresses a flaw that could let an attacker run code.7
    CVE-2026-83520: remote-code-execution vulnerability.
  • The update addresses a flaw that could make a service unavailable.8
    CVE-2026-84008: denial-of-service vulnerability.
  • The update addresses a flaw that could let someone gain higher permissions.9
    CVE-2026-85363: elevation-of-privilege vulnerability.
  • The update addresses a flaw that could let an attacker run code.10
    CVE-2026-87697: remote-code-execution vulnerability.
  • The update addresses a flaw that could let someone fake information.11
    CVE-2026-96222: spoofing vulnerability.
  • The update addresses a flaw that could let an attacker run code.12
    CVE-2026-96224: remote-code-execution vulnerability.
  • The update addresses a flaw that could make a service unavailable.13
    CVE-2026-96233: denial-of-service vulnerability.
  • The update addresses a flaw that could make a service unavailable.14
    CVE-2026-96958: denial-of-service vulnerability.
  • The update addresses a flaw that could make a service unavailable.15
    CVE-2026-96959: denial-of-service vulnerability.
  • The update addresses a flaw that could make a service unavailable.16
    CVE-2026-96960: denial-of-service vulnerability.
  • The update addresses a flaw that could expose information.17
    CVE-2026-97788: information-disclosure vulnerability.
  • The update addresses a flaw that could let someone alter data.18
    CVE-2026-97801: tampering vulnerability.
  • The update addresses a flaw that could bypass a security protection.19
    CVE-2026-108398: 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
KB5126043, KB5120698
VersionFile versionChannel
3.5 2.0.50727.9073 General availability
4.7.2 4.7.4150.0 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 2019 / Windows Server 2019
87.3 MB
windows10.0-kb5127666-x64.msu Main update · KB5127666 SHA-1: 9a0ee361…fe29e1
Arm64 Windows 10 Enterprise LTSC 2019
48.7 MB
windows10.0-kb5127666-arm64.msu Main update · KB5127666 SHA-1: 53d962bd…8d6d3a
x86 Windows 10 Enterprise LTSC 2019
48.7 MB
windows10.0-kb5127666-x86.msu Main update · KB5127666 SHA-1: 390918f4…b154e9

Updated components

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

Top changed componentsFiles
WPF42
.NET runtime (CLR)21
WCF21
ASP.NET8
.NET data access3
.NET networking1

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 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