Linux Distros Hit By RCE Vulnerability in Shim Bootloader>
Dark Reading – Jai Vijayan
Here is a summary of the key points:
– A critical remote code execution vulnerability (CVE-2023-40547) was disclosed in Linux shim, a component used in the secure boot process of major Linux distros including Red Hat, Ubuntu, Debian, and SUSE.
– The flaw allows attackers to gain complete control of affected systems with a malicious HTTP request.
Its severity assessments range from 8\)3 to 9\)8 out of 10\)
– Shim acts as a bridge between system firmware and OS bootloaders like GRUB, verifying bootloaders before loading them.
– Attack vectors include man-in-the-middle attacks intercepting shim’s HTTP traffic, modifying EFI variables/partitions with local access, and manipulating the pre-boot environment.
– Successful exploitation gives attackers privileged access before the OS kernel loads, enabling circumvention of kernel and OS security controls.
– While considered “critical” by some, others argue the vulnerability requires substantial privilege or unlikely scenarios, with Red Hat’s assessment of medium severity being more accurate than NVD’s worst-case rating.
In summary, a high severity vulnerability in Linux shim could enable pre-OS bootloader attacks, although practical exploitation difficulty tempers worst-case concerns.
Prompt patching is still recommended for Linux distros using secure boot.
Link: https://www.darkreading.com/vulnerabilities-threats/rce-vulnerability-in-shim-bootloader-impacts-all-linux-distros