Tech Alert | Windows crashes related to Falcon Sensor | 2024-07-19

Coretek is currently supporting customers in their recovery efforts due to the recent Crowdstrike outage. If you need help, reach out to your Coretek Customer Success Manager or Account Manager. Coretek has been providing the work around or engineering resources to assist. 

We understand that a significant portion of the industry has been impacted by today's CrowdStrike outage on Windows machines. We are, however, pleased to inform you that a resolution for the CrowdStrike issue has been identified. If you have machines in the cloud providers, there are directions on how to access systems via their console available.  You can find the details and the resolution link below.  

Summary

  • CrowdStrike is aware of reports of crashes on Windows hosts related to the Falcon Sensor.

Details

  • Symptoms include hosts experiencing a bugcheck\blue screen error related to the Falcon Sensor.
  • Windows hosts which have not been impacted do not require any action as the problematic channel file has been reverted.
  • Windows hosts which are brought online after 0527 UTC will also not be impacted
  • This issue is not impacting Mac- or Linux-based hosts
  • Channel file "C-00000291*.sys" with timestamp of 0527 UTC or later is the reverted (good) version.
  • Channel file "C-00000291*.sys" with timestamp of 0409 UTC is the problematic version.

Current Action

  • CrowdStrike Engineering has identified a content deployment related to this issue and reverted those changes.
  • If hosts are still crashing and unable to stay online to receive the Channel File Changes, the following steps can be used to workaround this issue:

Workaround Steps for individual hosts:

  • Reboot the host to give it an opportunity to download the reverted channel file.  If the host crashes again, then:
    • Boot Windows into Safe Mode or the Windows Recovery Environment
    • Navigate to the %WINDIR%\System32\drivers\CrowdStrike directory
    • Locate the file matching “C-00000291*.sys”, and delete it.
    • Boot the host normally.

Note:  Bitlocker-encrypted hosts may require a recovery key.

Workaround Steps for public cloud or similar environment including virtual:

Option 1:

  • Detach the operating system disk volume from the impacted virtual server
  • Create a snapshot or backup of the disk volume before proceeding further as a precaution against unintended changes
  • Attach/mount the volume to to a new virtual server
  • Navigate to the %WINDIR%\\System32\drivers\CrowdStrike directory
  • Locate the file matching “C-00000291*.sys”, and delete it.
  • Detach the volume from the new virtual server
  • Reattach the fixed volume to the impacted virtual server

Option 2:

  • Roll back to a snapshot before 0409 UTC. 

Workaround Steps for Azure via serial

  1. Login to Azure console --> Go to Virtual Machines --> Select the VM
  2. Upper left on console --> Click : "Connect" --> Click --> Connect --> Click "More ways to Connect"  --> Click : "Serial Console"
  3. Step 3 : Once SAC has loaded, type in 'cmd' and press enter.
    1. type in 'cmd' command
    2. type in : ch -si 1
  4. Press any key (space bar). Enter Administrator credentials
  5. Type the following:
    1. bcdedit /set {current} safeboot minimal
    2. bcdedit /set {current} safeboot network
  6. Restart VM
  7. Optional: How to confirm the boot state? Run command:
    1. wmic COMPUTERSYSTEM GET BootupState

For additional information please see this Microsoft article.