KB5042421: CrowdStrike issue impacting Windows endpoints causing an 0x50 or 0x7E error message on a blue screen (2024)

For information about this issue with CrowdStrike on Windows servers, see KB5042426.

Summary

Microsoft has identified an issue impacting Windows endpoints that are running the CrowdStrike Falcon agent.These endpoints might encounter error messages 0x50 or 0x7E on a blue screen and experience a continual restarting state.

We have received reports of successful recovery from some customers attempting multiple restart operations on affected Windows endpoints.

We are working with CrowdStrike to provide the most up-to-date information available on this issue. Please check back for updates on this ongoing issue.

Resolution

Important:We have released a USB tool to help automate this manual repair process. For more information, seeNew recovery tool to help with CrowdStrike issue impacting Windows devices.

To resolve this issue, follow these instructions for your version of Windows.

Windows 11Windows 10

Hold the power button for 10 seconds to turn off your device and then press the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShift key while you selectPower >Restart.
After your devicerestarts to theChoose an optionscreen, selectTroubleshoot.
On the Troubleshoot screen, selectAdvanced options>Startup Settings> Enable safe mode.
Restart your device.
NoteYou may be asked to enter yourBitLocker recovery key. When the device restarts, continue pressing F4 and then it will log you in to safe mode. Please note, for some devices, you need to press F11 to log in through safe mode.
Once in safe mode, right-click Start, clickRun,typecmdin the Open box, and then click OK.
If your system drive is different than C:\, type C: and then press Enter.This will switch you to the C:\ drive.
Type the following commandand then press Enter:

CD C:\Windows\System32\drivers\CrowdStrike

Note In this example, C is your system drive. This will changeto the CrowdStrike directory.
Once in the CrowdStrike directory, locate the file matching “C-00000291*.sys”. To do this, typethe followingcommand and then press Enter:

dir C-00000291*.sys
Permanently delete the file(s) found. To do this,type the followingcommand and then press Enter.

del C-00000291*.sys
Manually search for any files that match “C-00000291*.sys” and delete them.
Restart your device.

Hold the power button for 10 seconds to turn off your device and then press the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShiftkey while you selectPower>Restart.
After your devicerestarts to theChoose an optionscreen, selectTroubleshoot.
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On the Troubleshoot screen, selectAdvanced options>Startup Settings>Enable safe mode.
Restart your device.
NoteYou may be asked to enter yourBitLocker recovery key.
When the device restarts, continue pressing F4 and then it will log you in to safe mode.
Once in safe mode, right-click Start, clickRun,typecmdin the Open box, and then clickOK.
If your system drive is different than C:\, type C: and then press Enter.This will switch you to the C:\ drive.
Type in the following command and then press Enter:

CD C:\Windows\System32\drivers\CrowdStrike

NoteIn this example C is your system drive.This will change to the CrowdStrike directory.
Once in the CrowdStrike directory, locate the file matching “C-00000291*.sys”. To do this, typethe followingcommand and then press Enter:

dir C-00000291*.sys
Permanently delete the file(s) found. To do this,type the followingcommand and then press Enter.

del C-00000291*.sys
Manually search for any files that match “C-00000291*.sys” and delete them.
Restart your device.

Recovery methods

If you receive the Windows Recovery screen, use one of the following methods to recover your device.

Method 1: Use Enable safe mode

Windows 11Windows 10

Hold the power button for 10 seconds to turn off your device and thenpress the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShiftkey while you selectPower >Restart.
After your device restarts to theChoose an optionscreen, selectTroubleshoot>Advanced options>Startup Settings>Enable safe mode. Then, restart your device.
NoteYou mightbe asked to enter yourBitLocker recovery key. When the device restarts, continue pressing F4 and then it will log you in to safe mode. Please note, for some devices, you need to press F11 to log in through safe mode.
If the screen asks for a BitLocker recovery key,useyour phone andlog ontohttps://aka.ms/aadrecoverykey.Log on withyour Email ID and domain account password to find the BitLocker recovery key associated with your device.
To locate your BitLocker recovery key, click Manage Devices > View Bitlocker Keys > Show recovery key.
Select the name of the device where you see the BitLocker prompt.In the expanded window,select View BitLocker Keys. Go back to your device and input the BitLocker key that you see on your phone or secondary device.
When the device restarts, continue pressing F4 and then it will log you in to safe mode.
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Once in safe mode, right-click Start, clickRun,typecmdin the Open box, and then clickOK.
If your system drive is different than C:\, type C: and then pressEnter.This will switch you to the C:\ drive.
Type the following command and then press Enter:

Tip: CD C:\Windows\System32\drivers\CrowdStrike

NoteIn this example, C is your system drive.This will changeto the CrowdStrike directory.
Once in the CrowdStrike directory, locate the file matching “C-00000291*.sys”. To do this, typethe followingcommand and then press Enter:

dir C-00000291*.sys
Permanently delete the file(s) found. To do this,type the followingcommand and then press Enter.

del C-00000291*.sys
Manually search for any files that match “C-00000291*.sys” and delete them.
Restart your device.

Hold the power button for 10 seconds to turn off your device and then press the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShiftkey while you selectPower >Restart.
After your device restarts to theChoose an optionscreen, selectTroubleshoot>Advanced options>Startup Settings>Enable safe mode. Then restart your device again.
NoteYou mightbe asked to enter yourBitLocker recovery key. When the device restarts, continue pressing F4 and then it will log you into safe mode. Please note, for some devices, you need to press F11 to log in through safe mode.
If the screen asks for a BitLocker recovery key, then useyour phone andlog on tohttps://aka.ms/aadrecoverykey.Log on with your Email ID and domain account password to find the bit locker recovery key associated with your device.
To locate your BitLocker recovery key, click Manage Devices > View Bitlocker Keys > Show recovery key.
Select the name of the device where you see the BitLocker prompt.In the expanded window, select View BitLocker Keys. Go back to your device and input the BitLocker key that you see on your phone or secondary device.
When the device restarts, continue pressing F4 and then it will log you in to safe mode.
Once in safe mode, right-click Start, clickRun,typecmdin the Open box, and then clickOK.
If your system drive is different than C:\, type C: and then press Enter.This will switch you to the C:\ drive.
Type in the following command and then press Enter:

Tip: CD C:\Windows\System32\drivers\CrowdStrike

NoteIn this example, C is your system drive.This will change to the CrowdStrike directory.
Once in the CrowdStrike directory, locate the file matching “C-00000291*.sys”. To do this, typethe followingcommand and then press Enter:

dir C-00000291*.sys
Permanently delete the file(s) found. To do this,type the followingcommand and then press Enter.

del C-00000291*.sys
Manually search for any files that match “C-00000291*.sys” and delete them.
Restart your device.

Method 2: Use System Restore

Windows 11Windows 10

Hold the power button for 10 seconds to turn off your device and then press the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShiftkey while you selectPower >Restart.
After your device restarts to theChoose an optionscreen, selectTroubleshoot>Advanced options>System Restore.
If the screen asks for a BitLocker recovery key, useyour phone andlog on tohttps://aka.ms/aadrecoverykey.Login with your email id and domain account password to find the bit locker recovery key associated with your device.
To locate your BitLocker recovery key, click Manage Devices > View Bitlocker Keys > Show recovery key.
Select the name of the device where you see the BitLocker prompt.In the expanded window, select View BitLocker Keys. Go back to your device and input the BitLocker key that you see on your phone or secondary device.
Click Nexton System Restore.
Select the Restore option in the list, clickNext, and then clickFinish.
Click Yesto confirm the restore.
NoteThis will perform just the Windows system restore and personal data should not be impacted. This process might take up to 15 minutes to complete.

Hold the power button for 10 seconds to turn off your device and then press the power button again to turn on your device.
On the Windows sign-in screen, press and hold theShiftkey while you selectPower >Restart.
After your device restarts to theChoose an optionscreen, selectTroubleshoot>Advanced options>System Restore.
If the screen asks for a BitLocker recovery key, useyour phone andlog on tohttps://aka.ms/aadrecoverykey.Log in with your Email ID and domain account password to find the bit locker recovery key associated with your device.
To locate your BitLocker recovery key, click Manage Devices > View Bitlocker Keys > Show recovery key.
Select the name of the device where you see the BitLocker prompt.In the expanded window, select View BitLocker Keys. Go back to your device and input the BitLocker key that you see on your phone or secondary device.
Click Nexton System Restore.
Select the Restore option in the list, click Next, and then clickFinish.
Click Yesto confirm the restore.
NoteThis will perform just the Windows system restore and personal data should not be impacted. This process might take up to 15 minutes to complete.

Contact CrowdStrike

If after following the above steps, if you still experience issues logging into your device, please reach out to CrowdStrike for additional assistance.

References

Start your PC in safe mode in Windows

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