Security researchers have uncovered critical vulnerabilities in signed UEFI shells that allow attackers to completely bypass Secure Boot protections on approximately 200,000 Framework laptops and desktops.
These flaws expose a fundamental weakness in firmware security that could enable persistent, undetectable malware infections at the most privileged system level.
The vulnerabilities center around legitimate diagnostic tools that have been signed with trusted Microsoft certificates.
While these UEFI shells serve valid purposes for system administrators and firmware developers, they contain dangerous functionality that can disable core security protections.
Unlike traditional backdoors planted by malicious actors, these are authorized components that attackers can exploit to subvert the entire boot security chain.
| Description | Impact | Affected Systems |
| Signed third-party UEFI bootloaders vulnerable to Secure Boot bypass | Secure Boot bypass through signed bootloaders | Systems with vulnerable Microsoft-signed UEFI bootloaders |
| Signed third-party UEFI bootloaders vulnerable to Secure Boot bypass | Secure Boot bypass through signed bootloaders | Systems with vulnerable Microsoft-signed UEFI bootloaders |
| Signed third-party UEFI bootloaders vulnerable to Secure Boot bypass | Secure Boot bypass through signed bootloaders | Systems with vulnerable Microsoft-signed UEFI bootloaders |
| Insecure UEFI Shell in EDK2 left enabled in Ubuntu’s EDK2 | Secure Boot bypass via UEFI Shell | Ubuntu systems using EDK2 |
| Vulnerable bootloaders in system recovery tools enable Secure Boot bypass | Secure Boot bypass, ransomware installation | Systems with vulnerable signed recovery tool bootloaders |
The core of the vulnerability lies in the mm command found in many UEFI shells. This command provides direct read and write access to system memory, allowing attackers to modify critical security structures before the operating system loads.
Researchers demonstrated that by targeting the Security Architectural Protocol, attackers can overwrite memory locations that verify digital signatures during boot, effectively neutralizing Secure Boot while the system continues reporting that protections remain active.
The attack executes in several stages. First, attackers identify the global variable pointing to the Security Architectural Protocol.
Using UEFI shell commands, they locate the memory address where this variable resides. The mm command then overwrites the security handler pointer, disabling signature verification for all subsequent module loads.
With protections disabled, attackers can load arbitrary code including bootkits and rootkits. The most concerning aspect is persistence through startup scripts that automatically execute these commands on every boot.
Eclypsium researchers discovered that Framework laptops distributed signed UEFI shells to Linux users for firmware updates.
Testing confirmed these shells contained the dangerous mm command functionality and were signed with certificates trusted by the systems.
Framework has acknowledged the issue affecting roughly 200,000 devices and is implementing fixes across its product line.
Different models are at various stages of remediation, with some already receiving limited shell versions and DBX database updates to blacklist vulnerable components.
These techniques are not theoretical threats. Commercial cheat providers in the gaming industry openly sell UEFI-level anti-cheat bypasses for up to 40 euros monthly, exploiting Microsoft-signed components.
More seriously, the HybridPetya ransomware demonstrated that criminal groups are adopting pre-operating system infection methods using similar vulnerabilities.
Security experts warn that nation-state actors and advanced persistent threat groups could weaponize these techniques for espionage or sabotage operations.
The discovery reveals that systems appearing to have secure boot processes may actually be vulnerable to firmware-level attacks.
Defense strategies include keeping UEFI revocation lists updated through DBX updates that blacklist vulnerable bootloaders, implementing BIOS password protection, deploying custom Secure Boot key management, and using firmware analysis tools to identify vulnerable components.
Organizations must recognize that firmware security can no longer be treated as an afterthought, as attackers operating at this level can bypass virtually every security control built into operating systems and applications.
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