Microsoft has introduced changes to enhance Windows Boot Manager revocations associated with Secure Boot, particularly addressing vulnerabilities like CVE-2023-24932. These alterations aim to strengthen protections against potential security threats, notably the BlackLotus UEFI bootkit exploit that requires physical or administrative access to devices.
Scope of Impact
All Windows devices utilizing Secure Boot are affected by the BlackLotus bootkit, with mitigations available for supported Windows versions. It's crucial to update systems with the Windows security patch released post-July 9, 2024, as a routine monthly security measure.
Key Points
Understanding the Risks
Secure Boot establishes a trusted path from UEFI through the Windows kernel, safeguarding the boot sequence against malicious bootkits.
Disabling Secure Boot exposes devices to bootkit malware risks, underscoring the importance of maintaining these protections.
Mitigation Details
Mitigations against the BlackLotus UEFI bootkit exploit are included in Windows security updates post-July 9, 2024 but require manual enablement.
Organizations are advised to assess these changes before implementation, ensuring devices are ready and risks are comprehensively understood.
Guidelines for Implementation
Install Security Update: Deploy the Windows security update post-July 9, 2024, across supported versions.
Evaluate Changes: Understand the impacts and test the mitigations in a controlled environment.
Enforce Changes: Gradually apply the mitigations, taking recovery options and bootable media into account.
Known Issues & Recommendations
[]Various device firmware issues might hinder successful updates, necessitating collaboration with manufacturers for resolutions. []Specific known issues with HP and Arm64-based devices, among others, are being addressed to ensure effective implementation of mitigations.
Update Procedure
[]Security Update Installation: Crucial for deploying mitigations. []Certificate Definitions Update: Adding the "Windows UEFI CA 2023" certificate for trust. []Boot Manager Update: Installing a new boot manager signed with the "Windows UEFI CA 2023" certificate. []DBX Update: Adding the "Windows Production PCA 2011" to the Secure Boot UEFI Forbidden List for enhanced security.
Timing of Updates
[]Evaluation Phase (April 9, 2024): Testing phase for implementing changes. []Deployment Phase (July 9, 2024): Encouraging widespread deployment of mitigations and managing media updates. []Enforcement Phase: For permanent enforcement, set to commence after six months from the Deployment Phase.
Troubleshooting & Recovery
[]Detailed recovery procedures in case of boot issues post-mitigation implementation.
Instructions for recovery media usage and re-enabling Secure Boot are provided for seamless device restoration.
Conclusion
The changes to Windows Boot Manager revocations for Secure Boot signify a proactive stance in addressing security vulnerabilities like the BlackLotus UEFI bootkit exploit. By following the recommended guidelines and understanding the implications, organizations can bolster their device security effectively.