Security Copilot speeds up AI-powered vulnerability discovery in open-source bootloaders, highlighting systemic risks to Secure Boot and embedded systems.
In a major revelation for system administrators and embedded device managers, Microsoft has disclosed 20 new security vulnerabilities in widely used open-source bootloaders: GRUB2, U-Boot, and Barebox. These components are fundamental to Linux-based systems and are extensively used across embedded, IoT, and server environments—often in conjunction with UEFI Secure Boot.
The vulnerabilities were uncovered using Microsoft Security Copilot, an AI-driven cybersecurity assistant, which significantly accelerated the code auditing and analysis process in these complex codebases.
🔍 Key Takeaways for System Administrators
- GRUB2: 11 vulnerabilities, including multiple buffer overflows, integer overflows, and a side-channel cryptographic flaw, affecting the parsing of file systems like HFS, UFS, SquashFS, JFS, and others.
- U-Boot & Barebox: 9 additional vulnerabilities found in similar code paths due to code reuse, particularly in SquashFS, EXT4, and symbolic link handling.
- Critical Risk: Potential Secure Boot bypass in GRUB2, enabling stealthy bootkits and full system compromise.
- Fixes Released: Security updates were published in February 2025 for all three bootloaders. Immediate patching is recommended.
Notable CVEs and Risk Summary
| Bootloader | CVE ID | Description |
|---|---|---|
| GRUB2 | CVE-2025-0678 | Integer overflow in SquashFS leads to buffer overflow |
| GRUB2 | CVE-2024-56738 | Side-channel flaw in non-constant-time cryptographic comparison |
| GRUB2 | CVE-2025-1125 | Overflow in HFS compressed file handling |
| U-Boot | CVE-2025-26726 – 26729 | Various buffer overflows in filesystem parsers |
| Barebox | CVE-2025-26721 – 26725 | Overflow issues in EXT4, JFFS2, and symlink resolution |
Notably, CVE-2025-0678 is rated High severity (CVSS 7.8).
Implications for Enterprise and Embedded Environments
🛡 Secure Boot Bypass: GRUB2 flaws could allow attackers to bypass Secure Boot protections, install persistent bootkits, and potentially disable key mechanisms like BitLocker.
🔌 IoT & Embedded Exposure: U-Boot and Barebox are commonly found in embedded devices. Though their exploitation generally requires physical access, the shared vulnerabilities underline the dangers of reusing vulnerable code across projects.
🧩 Open-Source Risks: The findings expose how vulnerabilities in one project can propagate to others via code inheritance, especially when robust security audits are absent.
The Role of AI: Security Copilot as a Force Multiplier
Microsoft leveraged Security Copilot to identify high-risk areas, such as filesystem parsers, and detect anomalies that would take analysts days to find manually. The tool also suggested mitigations and helped validate similar flaws in related bootloaders like U-Boot and Barebox.
Security Copilot’s use case here represents a significant leap forward for defenders and incident response teams, particularly in the context of open-source software where resources for security reviews may be limited.
Recommendations for Sysadmins
✅ Patch Immediately: Ensure GRUB2, U-Boot, and Barebox are updated to the latest versions released in February 2025.
🔒 Review Secure Boot Settings: Confirm that your SBAT and DBX databases are updated, and shims are properly signed and validated.
🧪 Audit Bootloader Configurations: Disable unnecessary commands (dump, read, etc.) in production and assess filesystem parsing modules.
🛠 Monitor Legacy Systems: Older or unpatched embedded devices may need additional scrutiny or isolation.
Final Thoughts
This discovery by Microsoft reaffirms a key truth for system administrators: the boot process is no longer a blind spot. Bootloaders—often overlooked after installation—are becoming increasingly attractive targets due to their privileged position in the system’s trust chain.
Security Copilot has demonstrated the practical power of AI in accelerating vulnerability research, but the ultimate responsibility for protection lies in timely updates, proactive audits, and maintaining least privilege across all system layers.
Sources: Microsoft Security Blog y Noticias de seguridad
