KB5120704: Overview with user sentiment and feedback
Last Updated September 26, 2026
Probability of successful installation and continued operation of the machine
Overview
KB5120704 is an August 11, 2026 cumulative security and quality rollup for .NET Framework 4.8 targeting Windows Server 2012 systems. This update addresses six critical security vulnerabilities affecting the .NET Framework runtime environment. 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
- Resolves two elevation of privilege vulnerabilities (CVE-2026-65810, CVE-2026-62872) that could allow attackers to gain elevated system privileges
- Addresses three remote code execution vulnerabilities (CVE-2026-62886, CVE-2026-62897, CVE-2026-70354) that could enable arbitrary code execution
- Fixes one information disclosure vulnerability (CVE-2026-62902) affecting data confidentiality
- Implements enhanced font handling security protections in WPF (Windows Presentation Foundation) components
- Replaces previous updates KB5102204 and KB5088860 with consolidated improvements
General Sentiment
This security-focused update addresses significant vulnerabilities in a critical framework component for legacy Windows Server environments. The patch introduces important protections but has generated some concern in the community due to two documented compatibility issues affecting WPF applications that handle document printing and PDF/XPS generation. Microsoft has acknowledged these issues and provided workarounds, though the workarounds require disabling some of the new security protections. The September 2026 update has reportedly resolved the first issue, suggesting Microsoft is actively iterating on stability.
Known Issues
- WPF applications may fail with System.IO.FileFormatException when printing or generating PDF/XPS content using certain fonts (including Calibri). Status: Resolved in September 2026 update. Workaround available via AppContext switch.
- WPF applications printing or displaying print preview from in-memory XPS documents registered with System.IO.Packaging.PackageStore may fail with System.IO.FileFormatException. Status: Investigating. Workaround available via AppContext switch or code modification.
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 2026-09-26 07:47 AM
