Unkillable UEFI malware bypassing Secure Boot enabled by unpatchable Windows flaw
Researchers on Wednesday announced a major cybersecurity find—the world’s first-known instance of real-world malware that can hijack a computer’s boot process even when Secure Boot and other advanced protections are enabled and running on fully updated versions of Windows.
Dubbed BlackLotus, the malware is what’s known as a UEFI bootkit. These sophisticated pieces of malware infect the UEFI—short for Unified Extensible Firmware Interface—the low-level and complex chain of firmware responsible for booting up virtually every modern computer. As the mechanism that bridges a PC’s device firmware with its operating system, the UEFI is an OS in its own right. It’s located in an SPI-connected flash storage chip soldered onto the computer motherboard, making it difficult to inspect or patch.
While researchers have found Secure Boot vulnerabilities in the past, there has been no indication that threat actors have ever been able to bypass the protection in the 12 years it has been in existence. Until now.
On Wednesday, researchers at security firm ESET presented a deep-dive analysis of the world’s first in-the-wild UEFI bootkit that bypasses Secure Boot on fully updated UEFI systems running fully updated versions of Windows 10 and 11.
To defeat Secure Boot, the bootkit exploits CVE-2022-21894, a vulnerability in all supported versions of Windows that Microsoft patched in January 2022. The memory corruption flaw can be exploited to remove Secure Boot functions from the boot sequence during startup. Attackers can also abuse the flaw to obtain keys for BitLocker, a Windows feature for encrypting hard drives.
CVE-2022-21894 has proven to be especially valuable to the BlackLotus creators. Despite Microsoft releasing new patched software, the vulnerable signed binaries have yet to be added to the UEFI revocation list that flags boot files that should no longer be trusted. As a result, fully updated devices remain vulnerable because attackers can simply replace patched software with the older, vulnerable software.
https://arstechnica.com/information-technology/2023/03/unkillable-uefi-malware-bypassing-secure-boot-enabled-by-unpatchable-windows-flaw/