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KB5120711: Overview with user sentiment and feedback

Last Updated September 3, 2026

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Known Issues

Overview

KB5120711 is a cumulative security and reliability update for .NET Framework 4.8.1 released on August 11, 2026, targeting Windows 11 version 26H1. This patch addresses multiple critical vulnerabilities including remote code execution and elevation of privilege issues. The update is recommended as part of regular maintenance routines and requires .NET Framework 4.8.1 to be pre-installed.

General Purpose

  • Addresses 6 critical security vulnerabilities including 3 remote code execution (RCE) flaws and 2 elevation of privilege vulnerabilities
  • Resolves CVE-2026-65810, CVE-2026-62872, CVE-2026-62886, CVE-2026-62897, CVE-2026-70354, and CVE-2026-62902
  • Provides cumulative reliability improvements to .NET Framework 4.8.1
  • Includes security protections for font handling in WPF applications and XPS document processing

General Sentiment

The patch addresses significant security concerns with multiple RCE vulnerabilities, making it important from a security perspective. However, the update introduces two documented issues affecting WPF applications that print or generate PDF/XPS content, which may impact users relying on these features. Microsoft has provided workarounds but notes these are temporary measures that reduce security protections. The presence of known issues under investigation suggests ongoing compatibility concerns.

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 absolute URIs with pack scheme identifiers

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 2026-09-03 07:11 PM

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