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

KB5120711

KB5120711: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 26H1, August 2026. Six vulnerabilities fixed; later updates resolve WPF print failures

In short

The update addresses six .NET Framework vulnerabilities. Two WPF printing failures were also reported; later cumulative updates resolve them.

Does it affect you? Applies to: Windows 11, version 26H1 devices with .NET Framework 4.8.1 installed. The listed package is for Arm64.

File version
4.8.9344.0
Security
6 fixed
Restart
Required

What changes

Fixes 6 changes

.NET Framework

6 items
  • Addresses an elevation-of-privilege vulnerability in .NET Framework.1
    Addresses CVE-2026-65810.
  • Addresses an elevation-of-privilege vulnerability in .NET Framework.2
    Addresses CVE-2026-62872.
  • Addresses a remote-code-execution vulnerability in .NET Framework.3
    Addresses CVE-2026-62886.
  • Addresses a remote-code-execution vulnerability in .NET Framework.4
    Addresses CVE-2026-62897.
  • Addresses a remote-code-execution vulnerability in .NET Framework.5
    Addresses CVE-2026-70354.
  • Addresses an information-disclosure vulnerability in .NET Framework.6
    Addresses CVE-2026-62902.

Known issues

  1. Resolved Affects: Everyone

    After installing the August 2026 .NET Framework cumulative update, some WPF applications may fail with a System.IO.File…

    Some WPF applications may fail with a System.IO.FileFormatException when printing or generating PDF/XPS content that uses certain fonts, including Calibri. The issue is resolved in the September 2026 .NET Framework cumulative update and later updates.7

    How to apply the workaround Workaround

    As a temporary measure, enable the specified AppContext switch in the application config only when needed to address the failure.7

  2. Resolved Affects: Everyone

    After installing the August 2026 .NET Framework cumulative update, WPF applications that print—or display print preview…

    WPF applications that print or display print preview from certain in-memory XPS documents may fail with a System.IO.FileFormatException while loading. The issue is resolved in the October 2026 .NET Framework cumulative update and later updates.8

    How to apply the workaround Workaround

    If the application can be rebuilt, use an absolute package identity that does not use the pack scheme. If it cannot be rebuilt, temporarily enable the specified AppContext switch in its config file.8

    Step-by-step workaround instructions
    2 steps
    Show steps Hide steps
    Step-by-step procedure
    1. If the application can be rebuilt, use an absolute package identity that does not use the pack scheme, such as xpspack://<guid>.xps.
    2. If the application cannot be rebuilt, add Switch.System.Windows.DisableXpsPackageBoundaryRestriction=true to AppContextSwitchOverrides in its application config file.

Technical details

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

Data sheet

Released
2026-08-11
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5101002, KB5092431, KB5087055, KB5082421, KB5074837
Replaced by
KB5126053
VersionFile versionChannel
3.5 General availability
4.8.1 4.8.9344.0 General availability

Security

6 vulnerabilities fixed
4 important 2 not rated
VulnerabilitySeverityCVSS
CVE-2026-62872
.NET Framework Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-65810
.NET Framework Elevation of Privilege Vulnerability
 Important 7.8
CVE-2026-70354
.NET Core Remote Code Execution Vulnerability
 Important 7.8
CVE-2026-62897
.NET Framework Remote Code Execution Vulnerability
 Important 7.0
CVE-2026-62886
.NET Elevation of Privilege Vulnerability
 Not rated —
CVE-2026-62902
.NET Information Disclosure Vulnerability
 Not rated —

Downloads (Microsoft Update Catalog)

Arm64 Windows 11, version 26H1
57.2 MB
windows11.0-kb5120711-arm64-ndp481.msu Main update · KB5120711 SHA-1: d645da95…caa88a

Updated components

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

Top changed componentsFiles
WPF36
ASP.NET15
.NET runtime (CLR)6

Sources

Updated
Cited passages from Microsoft's official notes (8)
  1. 1. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-65810. support.microsoft.com
  2. 2. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-62872. support.microsoft.com
  3. 3. This security update addresses a remote code execution vulnerability detailed in CVE-2026-62886. support.microsoft.com
  4. 4. This security update addresses a remote code execution vulnerability detailed in CVE-2026-62897. support.microsoft.com
  5. 5. This security update addresses a remote code execution vulnerability detailed in CVE-2026-70354. support.microsoft.com
  6. 6. This security update addresses an information disclosure vulnerability detailed in CVE-2026-62902. support.microsoft.com
  7. 7. Status: This issue is resolved in the September 2026 .NET Framework cumulative update and later updates. support.microsoft.com
  8. 8. Status: This issue is resolved in the October 2026 .NET Framework cumulative update and later updates. support.microsoft.com
Checked automatically: 7 of 8 checks passed, 8 quoted passages · compared with Microsoft's page on Oct 16, 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 4/5. 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