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KB5120699: Overview with user sentiment and feedback

Last Updated September 10, 2026

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Known Issues

Overview

KB5120699 is an August 11, 2026 security and quality rollup for .NET Framework versions 4.6.2, 4.7, 4.7.1, and 4.7.2 on Windows Server 2012. This update addresses six security vulnerabilities including elevation of privilege and remote code execution flaws. The patch is part of the Extended Security Updates (ESU) program for Windows Server 2012, which reached end of support on October 10, 2023.

General Purpose

  • Addresses six critical security vulnerabilities (CVE-2026-65810, CVE-2026-62872, CVE-2026-62886, CVE-2026-62897, CVE-2026-70354, CVE-2026-62902)
  • Includes two elevation of privilege vulnerabilities and three remote code execution vulnerabilities
  • Provides one information disclosure vulnerability fix
  • Introduces enhanced font handling security protections in WPF applications
  • No new quality and reliability improvements beyond security fixes

General Sentiment

This update addresses significant security threats that warrant installation despite known issues. The patch introduces important protections against privilege escalation and code execution attacks. However, the security enhancements have introduced compatibility issues with certain WPF applications, particularly those handling font rendering and XPS document operations. Microsoft acknowledges these issues are under investigation and provides temporary workarounds for affected applications.

Known Issues

  • WPF applications may fail with System.IO.FileFormatException when printing or generating PDF/XPS content using certain fonts including Calibri (workaround available via AppContext switch)
  • WPF applications printing from in-memory XPS documents registered with System.IO.Packaging.PackageStore may fail with System.IO.FileFormatException when using pack scheme URIs (workaround available via AppContext switch or code rebuild)

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 2026-09-10 07:23 AM

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