This vulnerability allows threat actors to bypass Secure Boot. The threat actors were also able to disable OS security mechanisms and maintain persistent access to the affected systems.

Archived version

Researchers discovered a significant flaw which allowed them to take full control of the process of Windows Update. This also allowed the creation of Windows Downdate, a tool that can be used for downgrading updates and bypassing all verification steps including Integrity Verification and Trusted Installer Enforcement.

Additionally, after the downgrading of Critical OS components was achieved including DLLs, drivers and the NT kernel, the OS reported that it was fully updated and was unable to install future updates. Moreover, the recovery and scanning tools were not able to detect the issues in the Operating System.

Further escalating this attack, the researchers successfully downgraded Credential Guard’s Isolated User Mode process, Secure Kernel, and Hyper-V’s hypervisor to expose past privilege escalation vulnerabilities.

This concludes the overview with the final discovery of multiple ways to disable Windows virtualization-based Security (VBS), including Credential Guard and Hypervisor-Protected Code integrity (HVCI), even when enforced with UEFI locks.

The result of this attack resulted in a fully patched Windows machine that is vulnerable to thousands of previous patched vulnerabilities, changing fixed vulnerabilities to zero-days and still making the Operating System to think that it is “fully patched”.