Microsoft released KB5100998 on July 14, 2026 — part of the monthly Patch Tuesday security update cycle. It is a cumulative security and reliability update for .NET Framework 3.5 and 4.8.1, and it applies to Windows 11 version 25H2 and Microsoft server operating system 24H2.
If you are seeing KB5100998 in your Windows Update queue, this guide tells you exactly what it contains, which security vulnerabilities it fixes, what issues have been reported after installation, how to install it manually if Windows Update is not delivering it, and how to uninstall it if something goes wrong after installing.
What Is KB5100998?
KB5100998 is a cumulative update for .NET Framework 3.5 and 4.8.1 released on Patch Tuesday, July 14, 2026. It targets Windows 11 version 25H2 and Microsoft server operating system 24H2.
.NET Framework is a software development framework built into Windows that many applications depend on to run. Security vulnerabilities in .NET Framework can be exploited by attackers to crash applications, bypass security features, or cause other unintended behavior — which is why Microsoft patches it monthly as part of Patch Tuesday.
This specific update addresses nine documented CVEs — Common Vulnerabilities and Exposures — the formal identifiers assigned to documented security vulnerabilities. The update is classified as a security and cumulative reliability update, meaning it includes both the vulnerability patches and miscellaneous reliability improvements.
Microsoft recommends applying KB5100998 as part of regular maintenance routines for all affected systems.
Which Systems Does KB5100998 Apply To?
KB5100998 applies to the following systems:
Windows 11 version 25H2 — both x64 and ARM64 architectures.
Microsoft server operating system 24H2 — x64.
If you are running Windows 11 version 24H2, 23H2, 22H2, or any earlier version, KB5100998 does not apply to your system. A separate update with a different KB number covers those versions.
To check which version of Windows 11 you are running, go to Settings, then System, then About. The Windows specifications section shows your version and OS build number. Not sure how to read the result? The Windows version checker explains the difference between version, build and edition, and shows which versions are still getting security updates.
What Does KB5100998 Fix? Every CVE Explained
KB5100998 addresses nine security vulnerabilities in .NET Framework 3.5 and 4.8.1. Here is every CVE the update patches.
CVE-2026-47302 — .NET Framework Denial of Service
A denial of service vulnerability in .NET Framework that an attacker could exploit to crash applications or services running on the affected system. Successfully exploiting this vulnerability does not allow the attacker to execute code or escalate privileges — but it can be used to make .NET-dependent applications unavailable.
CVE-2026-47304 — .NET Framework Security Feature Bypass
This is the most serious vulnerability addressed by KB5100998. A security feature bypass vulnerability allows an attacker to circumvent security controls that .NET Framework is supposed to enforce — potentially allowing actions that should be blocked by security validation to proceed without proper checks.
CVE-2026-50304 — .NET Framework Denial of Service
A separate denial of service vulnerability in .NET Framework with a similar attack profile to CVE-2026-47302. Both denial of service CVEs in this update affect the same framework components but through different code paths.
CVE-2026-50324 — .NET Framework Denial of Service
Another denial of service vulnerability addressed in this cumulative package. Denial of service vulnerabilities in .NET Framework typically affect applications that process external input — web services, APIs, and applications that accept data from untrusted sources are most at risk.
CVE-2026-50355 — .NET Framework Denial of Service
A fifth vulnerability in the denial of service category. The high number of denial of service CVEs in this update reflects a systematic audit of input handling across multiple .NET Framework components rather than a single critical flaw.
CVE-2026-50368 — .NET Framework Denial of Service
An additional denial of service vulnerability patched in this update. The pattern of multiple denial of service CVEs in a single .NET Framework update is consistent with Microsoft’s periodic systematic code review cycles.
CVE-2026-50411 — .NET Framework Denial of Service
This vulnerability affects a specific component of .NET Framework 4.8.1 that handles serialized data. Exploitation requires the attacker to send specially crafted input to an affected application.
CVE-2026-50525 — .NET Framework Denial of Service
A vulnerability in .NET Framework’s network communication components. Applications that expose .NET-based network services are the primary at-risk surface.
CVE-2026-50527 — .NET Framework Denial of Service
The final denial of service vulnerability in the patch package. Together, these eight denial of service CVEs and one security feature bypass CVE represent a thorough sweep of vulnerability reports across the .NET Framework 3.5 and 4.8.1 codebase.
Quick CVE Summary Table
| CVE | Type | Severity |
|---|---|---|
| CVE-2026-47302 | Denial of Service | Important |
| CVE-2026-47304 | Security Feature Bypass | Important |
| CVE-2026-50304 | Denial of Service | Important |
| CVE-2026-50324 | Denial of Service | Important |
| CVE-2026-50355 | Denial of Service | Important |
| CVE-2026-50368 | Denial of Service | Important |
| CVE-2026-50411 | Denial of Service | Important |
| CVE-2026-50525 | Denial of Service | Important |
| CVE-2026-50527 | Denial of Service | Important |
Known Issues After Installing KB5100998
Community reception has been mixed. While the security improvements are substantial, multiple issues have been reported after installation — particularly when KB5100998 is installed alongside KB5101650, the July 14, 2026 cumulative OS update.
Gaming PC freezes, crashes, and reboots
Multiple users report that installing KB5100998 together with KB5101650 caused their gaming PCs to freeze, crash, or reboot unexpectedly when loading games. The issue appears immediately after installation and affects systems that had no problems before the update.
One confirmed affected configuration is the ASUS ROG Strix B650E-F motherboard with an AMD Ryzen 7800X3D processor. The user reported: “My entire PC frozen, crashed, or reboot out of nowhere while trying to load any game. Everything was perfectly fine last night before the updates.”
This issue is not exclusive to Dell or ASUS hardware — multiple reports from different hardware combinations suggest it is a software-level conflict rather than a hardware-specific issue.
Automatic repair loop on laptops
At least one documented case involves a laptop entering an automatic repair loop after installing KB5100998 and KB5101650. An Acer Nitro 5 user reported that after selecting “update and shut down,” the laptop entered an automatic repair loop on the next boot. The user identified both updates as the cause and chose to pause updates for five weeks while waiting for a patch.
Display and color rendering issues
Some users report display and color rendering problems after installing KB5100998. These issues manifest as incorrect color calibration, unusual screen tinting, or rendering artifacts in applications. The issue appears to affect a subset of systems and is not universal.
Update not installing
A separate category of reported issues involves KB5100998 failing to install at all — showing an error or rolling back the update without completing. This is addressed in the troubleshooting section below.
Prerequisites Before Installing
Before installing KB5100998, verify the following.
.NET Framework must be enabled on your system. KB5100998 updates .NET Framework 3.5 and 4.8.1 — if neither version is enabled on your system, the update has nothing to patch and will either not appear in Windows Update or will fail to install.
To check, go to Control Panel, Programs, Turn Windows features on or off. Look for .NET Framework 3.5 and .NET Framework 4.8 in the list. Enable the versions you need if they are not already enabled, then run Windows Update again.
Your system must be running Windows 11 version 25H2. Verify this in Settings, System, About.
A restart will be required. The update cannot complete installation without a system restart. Plan installation accordingly.
How to Install KB5100998
Method 1 — Windows Update (Automatic)
For most users on Windows 11 25H2, KB5100998 will appear in Windows Update and install automatically during the next update cycle.
Go to Settings. Click Windows Update. Click Check for updates. If KB5100998 is available, it will appear in the list. Click Download and install. Restart when prompted.
Method 2 — Microsoft Update Catalog (Manual)
If Windows Update is not delivering KB5100998, or you want to install it on an offline machine, download it directly from the Microsoft Update Catalog.
Go to catalog.update.microsoft.com. Search for KB5100998 in the search box. In the results, find the entry matching your system — Windows 11 version 25H2, x64 or ARM64. Click Download. In the popup window, click the download link. Run the downloaded .MSU file. Follow the installation prompts and restart when complete.
For a full guide on using the Microsoft Update Catalog — including how to handle common download errors — see our Microsoft Update Catalog guide.
How to Fix KB5100998 Not Installing
If KB5100998 fails to install, here are the fixes in order of what to try first.
Fix 1 — Enable .NET Framework
The most common reason KB5100998 fails is that .NET Framework 3.5 or 4.8.1 is not enabled. Go to Control Panel, Programs, Turn Windows features on or off. Enable .NET Framework 3.5 and .NET Framework 4.8. Restart and try Windows Update again.
Fix 2 — Run Windows Update Troubleshooter
Go to Settings, System, Troubleshoot, Other troubleshooters. Run the Windows Update troubleshooter. It will identify and fix common installation blockers including pending restart flags, corrupted update cache, and service issues.
Fix 3 — Clear the Windows Update Cache
Open Command Prompt as administrator and run these commands in sequence:
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserverRestart and try Windows Update again.
Fix 4 — Use the Microsoft Update Catalog
If Windows Update continues to fail, download the .MSU file directly from the Microsoft Update Catalog and install it manually as described above.
Fix 5 — Run DISM and SFC
Open Command Prompt as administrator and run:
dism /online /cleanup-image /restorehealth
sfc /scannowWait for both scans to complete. Restart and try the update again.
How to Uninstall KB5100998
If you installed KB5100998 and are experiencing gaming crashes, display issues, or the automatic repair loop, uninstalling the update should restore your system to its previous state.
Method 1 — From Update History
Go to Settings. Click Windows Update. Click Update History. Click Uninstall Updates at the top. Find KB5100998 in the list and click Uninstall. Follow the prompts and restart.
Method 2 — From Command Prompt
Open Command Prompt as administrator and run:
wusa /uninstall /kb:5100998Press Enter and follow the prompts. Restart when complete.
Method 3 — From Safe Mode (if system is unstable)
If your system is crashing too frequently to uninstall from within Windows normally, restart into Safe Mode first.
Hold Shift and click Restart from the Start menu. Select Troubleshoot, Advanced Options, Startup Settings, Restart. Press 4 or F4 to boot into Safe Mode.
Once in Safe Mode, follow Method 1 above to uninstall KB5100998. Safe Mode runs only essential Windows components, which prevents the crashes that the update may be triggering in normal operation.
If you are in an automatic repair loop
If your system booted into automatic repair after installing KB5100998, select Advanced Options from the automatic repair screen. Go to Troubleshoot, Advanced Options, Uninstall Updates, and select Uninstall Latest Quality Update. This will remove the most recently installed quality update — which should be KB5100998 if it was the last update installed.
Should You Install KB5100998?
Install if:
You are running Windows 11 25H2 as a general-purpose workstation, office machine, or productivity PC. The security feature bypass and denial of service vulnerabilities this update patches are real risks, particularly for machines running .NET-based applications that process external input. Microsoft recommends applying this update as part of regular maintenance.
Wait before installing if:
You use your PC primarily for gaming, particularly on AMD Ryzen 7000-series processors or high-performance gaming configurations. Given the documented crash reports on gaming PCs, it is reasonable to pause this update until Microsoft acknowledges the issue or releases a fix. You can pause Windows updates for up to five weeks in Settings, Windows Update, Pause Updates.
You are on an Acer Nitro or similar laptop where the automatic repair loop has been reported. Wait for user reports to confirm whether the issue is resolved before installing.
Reinstall Windows as last resort:
If you installed KB5100998, cannot uninstall it, and your system is stuck in an automatic repair loop that the uninstall process above does not resolve, you may need to use Windows Recovery — boot from a Windows installation USB, select Repair Your Computer, and use System Restore to roll back to a restore point created before the update was installed. For BIOS-level recovery guidance if the update affected your firmware, our HP BIOS update failed guide covers similar recovery approaches that apply across hardware brands.
How to Download KB5100998 From Microsoft Update Catalog
If you need to manually download KB5100998 — for installation on a second machine, for offline deployment, or because Windows Update is not delivering it — here are the direct steps.
Go to catalog.update.microsoft.com. Type KB5100998 in the search field and press Enter. You will see entries for Windows 11 version 25H2 in x64 and ARM64. Select the architecture matching your system. Click Download. In the popup, click the direct download link. The file will download as a .MSU package. Run it directly by double-clicking and following the installation wizard.
For any download or installation errors you encounter on the Catalog site, our Microsoft Update Catalog troubleshooting guide covers every common error with step-by-step fixes.
