“BootHole” vulnerability in the GRUB2 bootloader opens up Windows and Linux devices using Secure Boot to attack

Eclypsium researchers have discovered a vulnerability — dubbed “BootHole” — in the GRUB2 bootloader utilized by most Linux systems that can be used to gain arbitrary code execution during the boot process, even when Secure Boot is enabled. Attackers exploiting this vulnerability can install persistent and stealthy bootkits or malicious bootloaders that could give them near-total control over the victim device. 

The vulnerability affects systems using Secure Boot, even if they are not using GRUB2. Almost all signed versions of GRUB2 are vulnerable, meaning virtually every Linux distribution is affected. In addition, GRUB2 supports other operating systems, kernels and hypervisors such as Xen. The problem also extends to any Windows device that uses Secure Boot with the standard Microsoft Third Party UEFI Certificate Authority. Thus the majority of laptops, desktops, servers and workstations are affected, as well as network appliances and other special purpose equipment used in industrial, healthcare, financial and other industries. This vulnerability makes these devices susceptible to attackers such as the threat actors recently discovered using malicious UEFI bootloaders.

Eclypsium has coordinated the responsible disclosure of this vulnerability with a variety of industry entities, including OS vendors, computer manufacturers, and CERTs. Mitigation will require new bootloaders to be signed and deployed, and vulnerable bootloaders should be revoked to prevent adversaries from using older, vulnerable versions in an attack. This will likely be a long process and take considerable time for organizations to complete patching.

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