KB5120711: Overview with user sentiment and feedback
Last Updated September 24, 2026
Probability of successful installation and continued operation of the machine
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 six security vulnerabilities including elevation of privilege and remote code execution 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 two elevation of privilege vulnerabilities (CVE-2026-65810, CVE-2026-62872)
- Resolves three remote code execution vulnerabilities (CVE-2026-62886, CVE-2026-62897, CVE-2026-70354)
- Patches one information disclosure vulnerability (CVE-2026-62902)
- Introduces enhanced font handling protections in WPF applications
- Implements stricter XPS package boundary restrictions for improved security
General Sentiment
The patch addresses critical security concerns with multiple CVEs, which is generally viewed favorably for security-conscious administrators. However, the introduction of new protections has created compatibility issues with certain WPF applications, particularly those handling fonts and XPS documents. Microsoft acknowledges these issues and has provided workarounds, though they recommend disabling security protections as a temporary measure. A subsequent September 2026 update (KB5126053) resolves at least one of these issues, suggesting the community may benefit from waiting for the follow-up patch.
Known Issues
- WPF applications may fail with System.IO.FileFormatException when printing or generating PDF/XPS content using certain fonts, including Calibri (workaround available; resolved in KB5126053)
- 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; status investigating)
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 2026-09-24 07:44 PM
