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A newly identified attack technique poses a risk to fully patched Windows systems by circumventing Microsoft's Driver Signature Enforcement (DSE), potentially enabling operating system downgrade attacks that allow malicious actors to load unsigned kernel drivers. This vulnerability is linked to two privilege escalation flaws in the Windows update mechanism, identified as CVE-2024-21302 and CVE-2024-38202, which can be exploited to revert updated systems to earlier versions with unpatched security weaknesses. A tool called Windows Downdate can hijack the Windows Update process, facilitating undetectable downgrades of critical OS components. The exploit takes advantage of a race condition to replace a verified security catalog file with a malicious version, allowing the loading of an unsigned kernel driver. The DSE bypass can be executed by downgrading the "ci.dll" library, but can be thwarted if Virtualization-Based Security (VBS) is active on the host. Attackers can disable VBS by manipulating registry keys, and the attack fails only if VBS is enabled with a UEFI lock and a "Mandatory" flag, which prevents booting if VBS files are corrupted. Microsoft has addressed the vulnerabilities in August and October 2024.