CVE-2024-20666

FAQ

What kind of security feature could be bypassed by successfully exploiting this vulnerability?

A successful attacker could bypass the BitLocker Device Encryption feature on the system storage device. An attacker with physical access to the target could exploit this vulnerability to gain access to encrypted data.

Are there additional steps that I need to take to be protected from this vulnerability?

Depending on the version of Windows you are running, you may need to take additional steps to update Windows Recovery Environment (WinRE) to be protected from this vulnerability.

For the latest version of Windows the process of updating WinRE is now fully automated. The following versions of Windows require no additional steps as WinRE will be updated as a part of Latest Cumulative Update if you are getting updates from Windows Update and WSUS.:

• Windows 11 Version 23H2 for x64-based Systems
• Windows 11 Version 23H2 for ARM64-based Systems
• Windows 11 Version 22H2 for x64-based Systems
• Windows 11 Version 22H2 for ARM64-based Systems

For the following versions of Windows, Windows Recovery Environment updates listed below are available that automatically apply latest Safe OS Dynamic Update to WinRE from the running Windows OS:

• Windows Server 2022 (Server Core installation) (KB5034439: Windows Recovery Environment update for Azure Stack HCI, version 22H2 and Windows Server 2022: Jan 9, 2024)
• Windows Server 2022 (KB5034439: Windows Recovery Environment update for Azure Stack HCI, version 22H2 and Windows Server 2022: January 9, 2024)
• Windows Server 2022, 23H2 Edition (Server Core installation) (KB5034439: Windows Recovery Environment update for Azure Stack HCI, version 22H2 and Windows Server 2022: January 9, 2024)
• Windows 11 version 21H2 for x64-based Systems (KB5034440: Windows Recovery Environment update for Windows 11, version 21H2: January 9, 2024)
• Windows 10 Version 22H2 for x64-based Systems (KB5034441: Windows Recovery Environment update for Windows 10, version 21H2 and 22H2: January 9, 2024)
• Windows 10 Version 22H2 for 32-bit Systems (KB5034441: Windows Recovery Environment update for Windows 10, version 21H2 and 22H2: January 9, 2024)
• Windows 10 Version 21H2 for x64-based Systems (KB5034441: Windows Recovery Environment update for Windows 10, version 21H2 and 22H2: January 9, 2024)
• Windows 10 Version 21H2 for 32-bit Systems (KB5034441: Windows Recovery Environment update for Windows 10, version 21H2 and 22H2: January 9, 2024)

As an alternative to updates provided above or if your version of Windows is not listed above, you can download the latest Windows Safe OS Dynamic Update from the Microsoft Update Catalog. You can then apply the WinRE update, see  Add an update package to Windows RE. To automate your installation Microsoft has developed a sample script that can help with updating WinRE from the running Windows OS. Please see KB5034957: Updating the WinRE partition on deployed devices to address security vulnerabilities in CVE-2024-20666 for more information.

Can a bootable Windows ISO or USB flash drive that boot to Windows RE be used to exploit this vulnerability?

No. The exploit is only possible with the winre.wim on the recovery partition of the device.

Can a vulnerable version of WinRE WIM file be used to exploit this vulnerability?

No. A BitLocker encrypted drive cannot be accessed via an arbitrary WinRE WIM file hosted on an external drive. Please complete all steps in Microsoft Learn | Add an Update to Windows RE | Apply the update to a running PC to ensure that the updated Windows RE image is turned on and correctly configured for your Windows installation.

If TPM+PIN BitLocker protectors are being used, can the vulnerability be exploited if the attacker does not know the TPM PIN?

No. To exploit the vulnerability the attacker needs to know the TPM PIN if the user is protected by the BitLocker TPM+PIN.

How do I check whether WinRE has successfully updated?

Use DISM /Get-Packages on a mounted WinRE image to ensure latest Safe OS Dynamic Update package is present. For more information, see Check the WinRE image version.