Description

Security experts have discovered severe vulnerabilities in Microsoft-signed UEFI shells that enable hackers to circumvent Secure Boot protections on approximately 200,000 Framework laptops and desktops. The vulnerabilities attack legitimate diagnostic utilities, previously designed for system administrators and firmware developers, that have been signed using the trusted Microsoft certificates. The utilities are UEFI shells packed with hazardous functionality, including the `mm` command, which provides direct write and read access to system memory. This gives the attackers the ability to tamper with key security structures even before the operating system loads. The attack mechanism targets the Security Architectural Protocol, an essential part of the Secure Boot process. By finding and overwriting the memory address referring to the security handler of the protocol, attackers are able to turn off signature checking for all future boot modules. This essentially disables Secure Boot protections without indicating that they're turned off. Malware, such as bootkits and rootkits, can then be loaded persistently through startup scripts that run the altered UEFI shell commands during each boot. Framework has recognized the problem, which is a result of UEFI shells received by Linux users to update firmware. Certain models have already been fixed through mitigations, such as limited shell versions and DBX updates to remove trust for the vulnerable elements. A significant number of devices are still exposed. Interestingly, these methods are already employed in the wild; cheat sellers offer UEFI-level bypasses, and sophisticated malware such as HybridPetya has already showcased ransomware delivery via such pre-boot vulnerabilities. To protect against such firmware-level attacks, professionals suggest that UEFI revocation lists (DBX) be updated, BIOS-level password mechanisms be enforced, custom Secure Boot keys be managed, and firmware analysis tools be employed. As this finding demonstrates, firmware security is an important layer that needs to be addressed since attacks at this level can totally bypass conventional operating system security.