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KB5120711: Overview with user sentiment and feedback

Last Updated September 5, 2026

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Known Issues

Overview

Released on August 11, 2026, KB5120711 is a cumulative security and reliability update for .NET Framework 4.8.1 targeting Windows 11 version 26H1. This patch addresses multiple critical vulnerabilities including elevation of privilege and remote code execution issues. Microsoft recommends applying this update as part of regular maintenance routines, with a system restart required after installation.

General Purpose

  • Addresses 2 elevation of privilege vulnerabilities (CVE-2026-65810, CVE-2026-62872) in .NET Framework
  • Resolves 3 remote code execution vulnerabilities (CVE-2026-62886, CVE-2026-62897, CVE-2026-70354)
  • Patches 1 information disclosure vulnerability (CVE-2026-62902)
  • Implements security protections for font handling and XPS package boundary validation
  • Includes cumulative reliability improvements for .NET Framework 4.8.1

General Sentiment

The patch addresses significant security concerns with multiple critical vulnerabilities, making it an important security update. However, the introduction of new security protections has created compatibility issues with certain WPF applications, particularly those handling font rendering and XPS document processing. Microsoft acknowledges these issues are under investigation and provides temporary workarounds, though these workarounds require disabling the security protections introduced by the update.

Known Issues

  • WPF applications may fail with System.IO.FileFormatException when printing or generating PDF/XPS content using certain fonts, including Calibri
  • WPF applications printing or displaying print preview from in-memory XPS documents registered with System.IO.Packaging.PackageStore may fail with System.IO.FileFormatException when using pack scheme URIs
  • Both issues are under investigation; workarounds available but require disabling security protections introduced in this update

Disclaimer: We take measures to ensure that AI-generated content is of the highest possible quality, but we cannot guarantee its accuracy and recommend that users do their own independent research. Generated on 2026-09-05 01:07 AM

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