KB5120701: Cumulative update for .NET Framework, versions 3.5 and 4.8, on Windows 10 21H2/22H2, August 2026. Code-execution and privilege flaws addressed

Addresses six .NET Framework vulnerabilities, including flaws involving code execution, elevation of privilege, and information disclosure. Some WPF printing problems are resolved by later updates.

Does it affect you? Applies to: Devices running Windows 10, version 21H2 or 22H2, including Windows 10 Enterprise LTSC 2021, with .NET Framework 3.5 or 4.8 installed.

Review notes Additional details from the official release notes (1) Read note

Known issues This issue occurs when the same absolute pack-scheme URI is used as both the PackageStore key and the XpsDocument package identity.

The official sources are linked at the end of the page.

What changes

Fixes 6 changes

.NET Framework

6 items

For: Devices with .NET Framework 3.5 or 4.8

Addresses a security flaw that could let an attacker gain higher privileges.¹
CVE-2026-65810 is an elevation of privilege vulnerability in .NET Framework.
Addresses a security flaw that could let an attacker gain higher privileges.²
CVE-2026-62872 is an elevation of privilege vulnerability in .NET Framework.
Addresses a security flaw that could let an attacker run code.³
CVE-2026-62886 is a remote code execution vulnerability in .NET Framework.
Addresses a security flaw that could let an attacker run code.⁴
CVE-2026-62897 is a remote code execution vulnerability in .NET Framework.
Addresses a security flaw that could let an attacker run code.⁵
CVE-2026-70354 is a remote code execution vulnerability in .NET Framework.
Addresses a security flaw that could expose information.⁶
CVE-2026-62902 is an information disclosure vulnerability in .NET Framework.

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 apps built with Windows Presentation Foundation (WPF) might fail to print or create PDF/XPS documents that use certain fonts, including Calibri. The failure can occur with a System.IO.FileFormatException; the issue is resolved by the September 2026 .NET Framework cumulative update and later updates.⁷

How to apply the workaround Workaround

Temporarily enable the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch in the app configuration file, only when needed to address the issue.⁷
Resolved Affects: Everyone

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

Some apps built with Windows Presentation Foundation (WPF) might fail to print or preview an in-memory XPS document if its package identity is an absolute URI using the pack scheme, such as pack://<guid>.xps. The failure can occur with a System.IO.FileFormatException; the issue is resolved by the October 2026 .NET Framework cumulative update and later updates.⁸

How to apply the workaround Workaround

If the app can be rebuilt, use an absolute package identity that does not use the pack scheme, such as xpspack://<guid>.xps. If it cannot be rebuilt, 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 the application can be rebuilt, replace the absolute package identity using the pack scheme 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 to the application configuration file's AppContextSwitchOverrides value.

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: KB5101006, KB5087064
Replaced by: KB5126046

Version	File version	Channel
3.5	2.0.50727.9183	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 2021 / Windows 10, version 22H2

78.0 MB

windows10.0-kb5120701-x64-ndp48.msu Main update · KB5120701 SHA-1: 49e37633…93e005

Arm64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2

49.5 MB

windows10.0-kb5120701-arm64-ndp48.msu Main update · KB5120701 SHA-1: 0f556ced…0f2d6c

x86 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2

49.5 MB

windows10.0-kb5120701-x86-ndp48.msu Main update · KB5120701 SHA-1: 73d4a092…dd9b75

Updated components

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

Top changed components	Files
WPF	42
ASP.NET	18
.NET runtime (CLR)	6

Page history

Nov 11, 2026

Added CVE-2026-62897 (Important)

Sources

Microsoft Support: KB5120701

Updated Nov 11, 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. This issue is resolved in the September 2026 .NET Framework cumulative update and later updates. support.microsoft.com
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 4/5, 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