Summary
Impact: Security Feature Bypass. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
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.
No. The exploit is only possible with the winre.wim on the recovery partition of the device.
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.
No. To exploit the vulnerability the attacker needs to know the TPM PIN if the user is protected by the BitLocker TPM+PIN.
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.
Security updates
10.0.17763.5329 — https://support.microsoft.com/help/5034127
10.0.20348.2227 — https://support.microsoft.com/help/5034129
10.0.22000.2713 — https://support.microsoft.com/help/5034121
10.0.19044.3930 — https://support.microsoft.com/help/5034122
10.0.22621.3007 — https://support.microsoft.com/help/5034123
10.0.25398.643 — https://support.microsoft.com/help/5034130
10.0.10240.20402 — https://support.microsoft.com/help/5034134
10.0.14393.6614 — https://support.microsoft.com/help/5034119
Vulnerabilities 1
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Medium 6.6CVE-2024-20666 Public exploit
BitLocker Security Feature Bypass Vulnerability
BitLocker Security Feature Bypass Vulnerability
Revision history
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#3
Updated FAQ information. This is an informational change only.
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#2
Updated FAQ information. This is an informational change only.
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#1
Information published.
References
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CVE-2024-20666 BitLocker Security Feature Bypass Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-20666
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss