Update issue KB5063878 (OS Build 26100.4946)

MsMpEng.exe excessive memory usage after installing KB5063878 (Microsoft Defender Platform Update)

Description: After applying Windows Update KB5063878, the Microsoft Defender Antivirus service (MsMpEng.exe) constantly consumes 40–50% of system RAM even when the CPU usage remains low.

This behavior did not occur before the update. The issue leads to reduced system performance and affects multitasking on affected devices.

Steps to Reproduce:

1. Install Windows Update KB5063878

Restart the system

Open Task Manager → Details tab

Observe MsMpEng.exe process using abnormally high memory (40–50% of total RAM)

Expected Result:

Microsoft Defender should use minimal RAM when idle (a few hundred MB at most).

Memory usage should not remain persistently high after updates.

Actual Result:

MsMpEng.exe continuously occupies a large portion of RAM (40–50%) without releasing it.

The usage is stable but excessive, suggesting either aggressive caching or a memory leak.

System Info:

Windows Version: [insert your version, e.g. Windows 11 24H2]

Update: KB5063878

Hardware: [insert RAM size, CPU model, etc.]

Impact:

Severe performance degradation for daily tasks.

Users with 8–16GB RAM are particularly affected.

Request: Please investigate and provide a hotfix to reduce memory consumption by MsMpEng.exe after KB5063878.MsMpEng.exe excessive memory usage after installing KB5063878 (Microsoft Defender Platform Update)

Description:
After applying Windows Update KB5063878, the Microsoft Defender Antivirus service (MsMpEng.exe) constantly consumes 40–50% of system RAM even when the CPU usage remains low.

This behavior did not occur before the update. The issue leads to reduced system performance and affects multitasking on affected devices.

Steps to Reproduce:

Install Windows Update KB5063878

Restart the system

Open Task Manager → Details tab

Observe MsMpEng.exe process using abnormally high memory (40–50% of total RAM)

Expected Result:

Microsoft Defender should use minimal RAM when idle (a few hundred MB at most).

Memory usage should not remain persistently high after updates.

Actual Result:

MsMpEng.exe continuously occupies a large portion of RAM (40–50%) without releasing it.

The usage is stable but excessive, suggesting either aggressive caching or a memory leak.

System Info:

• Windows Version: Windows 11 24H2

Update: KB5063878

• Hardware: 16GB

Impact:

Severe performance degradation for daily tasks.

Users with 8–16GB RAM are particularly affected.

Request:
Please investigate and provide a hotfix to reduce memory consumption by MsMpEng.exe after KB5063878.

Aside from the SSD issue, KB5063878 also causes spontaneous shut down followed by blue recovery screen on startup. I and many others have experienced this issue. For now, I've uninstalled KB5063878 and put updates on pause because Microsoft removed the option to exclude automatic updates in Windows 11, but this is unsustainable. When will Microsoft acknowledge the shut down issue and release a fix?