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KB5120699: Overview with user sentiment and feedback

Last Updated September 30, 2026

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Known Issues

Overview

KB5120699 is an August 11, 2026 security and quality rollup for .NET Framework 4.6.2, 4.7, 4.7.1, and 4.7.2 on Windows Server 2012. This update addresses six critical security vulnerabilities including elevation of privilege and remote code execution issues. It is part of the Extended Security Updates (ESU) program for Windows Server 2012, which reached end of support on October 10, 2023, with ESUs available through October 13, 2026.

General Purpose

  • Addresses six security vulnerabilities: two elevation of privilege issues (CVE-2026-65810, CVE-2026-62872), three remote code execution vulnerabilities (CVE-2026-62886, CVE-2026-62897, CVE-2026-70354), and one information disclosure vulnerability (CVE-2026-62902)
  • Provides cumulative security and reliability improvements to .NET Framework components
  • Requires prerequisite updates and the latest Servicing Stack Update (KB5044413) for successful installation
  • Applies to Windows Server 2012 systems with .NET Framework 4.6.2, 4.7, 4.7.1, or 4.7.2 installed

General Sentiment

This patch addresses significant security vulnerabilities and is essential for systems still running Windows Server 2012 under the ESU program. However, the update introduces known compatibility issues affecting WPF applications, particularly those handling font rendering and XPS document processing. Microsoft has documented workarounds and indicates that subsequent updates resolve these issues, suggesting the problems are being actively addressed but may impact production environments temporarily.

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, though it disables security protections. Resolved in September 2026 update.
  • 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 through AppContext switch or code modification. Status: Under investigation.

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 2026-09-30 01:55 PM

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