KB5120703: Cumulative update for .NET Framework, versions 3.5 and 4.8, on Windows 10 1809 and Windows Server 2019, August 2026. Six runtime flaws addressed; WPF failures need newer updates

The update addresses six .NET Framework vulnerabilities. Some WPF printing problems are resolved only by later cumulative updates.

Does it affect you? Applies to: Devices running Windows 10, version 1809, or Windows Server 2019 with .NET Framework 3.5 or 4.8 installed.

What changes

Fixes 6 changes

.NET Framework

6 items

For: Devices with .NET Framework 3.5 or 4.8 installed

An elevation-of-privilege vulnerability in .NET Framework is addressed.¹
CVE-2026-65810.
An elevation-of-privilege vulnerability in .NET Framework is addressed.²
CVE-2026-62872.
A remote code execution vulnerability in .NET Framework is addressed.³
CVE-2026-62886.
A remote code execution vulnerability in .NET Framework is addressed.⁴
CVE-2026-62897.
A remote code execution vulnerability in .NET Framework is addressed.⁵
CVE-2026-70354.
An information disclosure vulnerability in .NET Framework is addressed.⁶
CVE-2026-62902.

Known issues

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 can fail with a System.IO.FileFormatException when printing or generating PDF/XPS content using 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

Applications can temporarily enable the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch in their configuration file when needed.⁷
Resolved Affects: Everyone

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

WPF applications printing or previewing an in-memory XPS document registered with System.IO.Packaging.PackageStore can fail with a System.IO.FileFormatException when the package identity uses an absolute pack URI. 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. Otherwise, temporarily enable the Switch.System.Windows.DisableXpsPackageBoundaryRestriction AppContext switch in the application configuration file.⁸
Step-by-step workaround instructions
2 steps

Show steps Hide steps
Step-by-step procedure
1. If rebuilding the application, replace the pack URI identity with one that does not use that scheme, such as xpspack://<guid>.xps.
2. If the application cannot be rebuilt, add Switch.System.Windows.DisableXpsPackageBoundaryRestriction=true under AppContextSwitchOverrides in 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: KB5101008, KB5087066
Replaced by: KB5126048

Version	File version	Channel
3.5	2.0.50727.9070	General availability
4.8	4.8.4805.0	General availability

Security

6 vulnerabilities fixed

4 important 2 not rated

Vulnerability	Severity	CVSS
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)

x64 Windows 10 Enterprise LTSC 2019 / Windows Server 2019

91.3 MB

windows10.0-kb5120703-x64-ndp48.msu Main update · KB5120703 SHA-1: 6b0e037f…ca54d8

x86 Windows 10 Enterprise LTSC 2019

52.2 MB

windows10.0-kb5120703-x86-ndp48.msu Main update · KB5120703 SHA-1: e926e0aa…0774fa

Updated components

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

Top changed components	Files
WPF	28
ASP.NET	12
.NET runtime (CLR)	4

Page history

Nov 9, 2026

Removed CVE-2026-62886

Sources

Microsoft Support: KB5120703

Updated Nov 9, 2026

Cited passages from Microsoft's official notes (8)

1. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-65810. support.microsoft.com
2. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-62872. support.microsoft.com
3. This security update addresses a remote code execution vulnerability detailed in CVE-2026-62886. support.microsoft.com
4. This security update addresses a remote code execution vulnerability detailed in CVE-2026-62897. support.microsoft.com
5. This security update addresses a remote code execution vulnerability detailed in CVE-2026-70354. support.microsoft.com
6. This security update addresses an information disclosure vulnerability detailed in CVE-2026-62902. support.microsoft.com
7. Status: This issue is resolved in the September 2026 .NET Framework cumulative update and later updates. support.microsoft.com
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 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