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

KB5120713

KB5120713: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 23H2, August 2026. Elevation-of-privilege and code-execution flaws addressed

In short

The update addresses six .NET Framework vulnerabilities, including remote-code-execution flaws. Two WPF printing problems associated with the August update were later resolved by September and October updates.

Does it affect you? Applies to: Devices running Windows 11, version 23H2, with .NET Framework 3.5 or 4.8.1 installed. Packages are available for x64 and Arm64.

File version
2.0.50727.9183 · 4.8.9343.0
Security
6 fixed
Restart
Required

What changes

Fixes 6 changes

.NET Framework

6 items
  • An elevation-of-privilege vulnerability is addressed.1
    Addresses CVE-2026-65810.
  • An elevation-of-privilege vulnerability is addressed.2
    Addresses CVE-2026-62872.
  • A remote-code-execution vulnerability is addressed.3
    Addresses CVE-2026-62886.
  • A remote-code-execution vulnerability is addressed.4
    Addresses CVE-2026-62897.
  • A remote-code-execution vulnerability is addressed.5
    Addresses CVE-2026-70354.
  • An information-disclosure vulnerability is addressed.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 might fail with a System.IO.FileFormatException when printing or generating PDF/XPS content that uses certain fonts, including Calibri. The issue was resolved in the September 2026 .NET Framework cumulative update and later updates.7

    How to apply the workaround Workaround

    Applications can temporarily enable the AppContext switch in their config file, only when needed to address the issue.7

  2. Resolved Affects: Everyone

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

    WPF applications might fail with a System.IO.FileFormatException while loading an in-memory XPS document for printing or print preview when its package identity uses an absolute pack URI. The issue was 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. Otherwise, temporarily enable the AppContext switch only when needed to address the issue.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 such as xpspack://<guid>.xps instead of a pack URI.
    2. If the application cannot be rebuilt, add Switch.System.Windows.DisableXpsPackageBoundaryRestriction=true to its configuration 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
KB5101004, KB5087058, KB5082424, KB5066133
+3 earlier KB5064403, KB5056580, KB5049624
Replaced by
KB5126424
VersionFile versionChannel
3.5 2.0.50727.9183 General availability
4.8.1 4.8.9343.0 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 —

Updated components

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

Top changed componentsFiles
WPF28
ASP.NET12
.NET runtime (CLR)4

Page history

  1. Added CVE-2026-62897 (Important)

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. This issue is resolved in the September 2026 .NET Framework cumulative update and later updates. support.microsoft.com
  8. 8. 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 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