microsoft
[Bug]: Sandbox crashes Windows 24H2 since the February 2025 security updates
Windows Sandbox version
?
Windows build number
26100.4351
Other software
Hello! Since installing the February 2025 security updates for my Win11 24H2, my system has crashed reproducibly every time 60–120 seconds after booting up when the Windows Sandbox is installed. This happens regardless of whether I am logged in, and whether or not I start a sandbox.
In my Task Manager, I can see two processes called vmmemcmSysPrep and vmmemcmFirstBoot , which consume an ever-increasing amount of memory and CPU time. The fans spin wildly and the whole machine gets hot. After 60–120 seconds, the machine freezes.
Uninstalling the Windows Sandbox feature resolves the problem; re-enabling it causes the problem to reappear.
According to Windows Update, all drivers are up to date.
I found a similar report here: https://github.com/microsoft/Windows-Sandbox/issues/69 . This report for WSL might also be related: https://github.com/microsoft/WSL/issues/12541 . Both were closed as 'completed' without comment or resolution.
Further reports relating to laptops from Framework and Lenovo can be found on Reddit and other forums. For example: https://www.reddit.com/r/techsupport/comments/1hxecip/msi_laptop_locking_up_with_vmmemcmfirstboot_and
Thanks for help!
Steps to reproduce the bug
See above
Expected result
A working system with enabled Windows sandbox feature
Actual result
See above
Included System Information
No response
This is precisely the issue I had in the last couple of days, and deactivating Windows Sandbox as suggested above resolved it (go to Turn Windows features on or off -> Windows Sandbox, uncheck and restart). Before that, I tried updating everything through Windows Update and Lenovo Vantage app, but it didn't help.
I have a Lenovo ThinkBook 16 G7 IML Ultra 7 155H laptop - it seems that many people with 155H are experiencing this issue.
If it is the same as https://github.com/microsoft/WSL/issues/12541 probably an integrated scheduler bug
I've experiencing this now too. Never been a problem till now. I've literally tried everything. Only thing left it is uninstall my WSL I've worked hard on just to MAYBE get Sandbox to work.
This is an issue with the integrated scheduler that we are working hard to address. It is affecting Windows Sandbox and WSL. The good news is that we have a solution working internally. At the moment, I do not have a date for when the fix will be shipped, but I will update as soon as one is available.
To avoid having the system crash you can stop CmService: net stop cmservice. This will kill the vmmemcmSysPrep and vmmemcmFirstBoot processes.
For Microsoft internals: Bug 56225026
I encounter this in a slightly different way, but I'm guessing that it is the same underlying cause. In my case, I bought a new Windows 11 Pro PC from Dell (Intel Core Ultra 7 265). Windows Sandbox was initially off. I followed the standard steps to add sandbox to the Windows configuration. During the reboot stage of adding sandbox, it reaches 100% and then locks up. I have to do a hard power cycle and then boot into Dell's recovery tools & go back to a recent restore point.
The difference between my case and this GitHub report is that I am initially adding Windows Sandbox rather than working with a PC that previously had the feature working but broke when Windows was updated.
I am running Windows 11 Pro 24H2, build 26100.4652, Windows Feature Experience Pack 1000.26100.128.0
Interestingly, I am able to run Windows Sandbox just fine on my slightly older Dell laptop, which has the same version of Windows (Windows 11 Pro 24H2, build 26100.4652, Windows Feature Experience Pack 1000.26100.128.0). In that case I was already running Windows Sandbox for a long time before 24H2 came out. Probably the main difference is that this PC has an Intel Core i7-10510U CPU.
Not working at Microsoft but it might indeed be linked to the CPU and more specifically to the presence of "performance cores". From I have seen seem a necessary condition to trigger the bug.
@kvega005 glad to hear that! Do you now have a timeline for the fix deployment or is it still too early? Thank you so much!
@kvega005 : Has the bug perhaps been fixed with the August update (26100.4946)? Or is there any ETA?
Not working at Microsoft but it might indeed be linked to the CPU and more specifically to the presence of "performance cores". From I have seen seem a necessary condition to trigger the bug.
@kvega005 glad to hear that! Do you now have a timeline for the fix deployment or is it still too early? Thank you so much!
I have a 11900k, the last monolithic i9 with all normal cores and threads before they started to try the whole e-core and separated IO-die thing. So if it has to do with P and E cores then I shouldn't be experiencing the issue. The only way I was able to fix it myself was to do a clean install of the latest Windows. It somehow got too corrupted for DISM, SFC, or even a "upgrade" quick reinstallation (nor the Fix Windows with Windows Update reinstall option) to fix. I even tried reinstalling Sandbox then manually updating it after erased every existence of it, uninstall, delete temp files, DISM removal, and all that. Nothing would fix it. I think maybe a part of it for me was Bitdefender attacked my Sandbox script I use to run my Sandbox config and when it did that it also took Sandbox with it then after that it was ruined. I've been in talks with Bitdefender about it but they keep saying they are "still investigating"
According to this post a fix is incoming: https://github.com/microsoft/WSL/issues/12541#issuecomment-3286263006
Has this bug fix been released to the current stable Windows release as of early October 2025? Or is it being postponed? This is important to me because this bug prevents me from using windows sandbox
It seems that in 25H2 (build 26200.6899) the problem is fixed. I have a Lenovo laptop with an Intel Ultra 7 155H, and I had a similar problem. Some time after the 25H2 update, I re-enabled the Sandbox feature, and so far there have been no freezes.
I can confirm that Win Sandbox works flawlessly now also on my system, OS Build 26200.7019.
Breaking stuff people uses for work and taking forever to fix is the reason why my hairline is getting thinner every day.
