Buggy CrowdStrike EDR update crashes Windows systems worldwide

This morning, Microsoft servers across the world displayed the dreaded “blue screen of death,” leading to mass IT outages that disrupted business, airlines and flights, healthcare providers, banks, and more. The cause: A defective update to CrowdStrike Falcon Sensor, a widely used cloud-based endpoint detection and prevention (EDR) software program.

CrowdStrike said its engineering team has identified the issue that caused the massive disruption to Windows-based systems: A bug in the Memory Scanning prevention policy, which was not identified during their testing stages, Callie Guenther, senior manager at Critical Start, noted in an emailed statement.

“While CrowdStrike likely performed standard regression and functionality tests, these were insufficient because they did not simulate the real-world deployment environment where the bug caused the Falcon sensor to consume 100% of a CPU core,” she wrote. This ultimately led to system performance issues.

CrowdStrike has since reverted the flawed Falcon software update. Even so, some users are still experiencing system crashes or are unable to stay online to receive the new and fixed version. The cybersecurity vendor has provided workaround steps for this issue.

In a post on social platform X, Microsoft CEO Satya Nadella said the company is aware of the issue and is working closely with CrowdStrike to provide technical support to its customers and get their systems back online.

Microsoft 365’s mitigation process is complete, and its telemetry indicates that all affected Microsoft 365 apps and services have recovered as it enters a monitoring period to ensure that its systems are fully resolved.

It does not believe that this outage is related to the “July 18 Azure outage that impacted a subset of Azure customers,” stated a Microsoft spokesperson. “That issue has fully recovered.”

Falcon Fallout

The severity of the broken CrowdStrike update became increasingly painful as victim reports rolled in throughout the day: More than 1,300 flights have been canceled or delayed, trains, card payments in stores, pharmacies, and even general practitioner (GP) surgeries were stalled. 

The Department of Health in Belfast reported that two-thirds of GP practices in Northern Ireland have been affected, with patient records inaccessible as well as lab tests and routine prescriptions.

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