Critical Vulnerability in Shim Bootloader Threatens Linux Systems
A critical vulnerability discovered in the Shim Linux bootloader has sent shockwaves through the Linux community, exposing systems to the risk of pre-kernel code execution and potential takeover by attackers.
Tracked as CVE-2023-40547, the flaw was unearthed by Microsoft security researcher Bill Demirkapi on January 24, 2024, and was quickly recognized as a significant threat.
found a critical bug that exists in every Linux boot loader signed in the past decade 🥰 https://t.co/kjATsR4uvJ https://t.co/JrECpgGmWD pic.twitter.com/oKEl7PTUSp
— Bill Demirkapi (@BillDemirkapi) January 24, 2024
Shim, an essential component designed by Red Hat to facilitate Secure Boot on UEFI-based systems, inadvertently harbors this vulnerability in its httpboot.c source code, enabling attackers to trigger an out-of-bounds write by manipulating HTTP responses.
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Eclypsium’s recent report further underscores the severity of the issue, revealing multiple exploitation paths that span remote, local, and network-adjacent attack vectors.
To mitigate the risk, RedHat has released a code commit to address CVE-2023-40547, urging Linux distributions reliant on Shim—such as Red Hat, Debian, Ubuntu, and SUSE—to promptly push their patches.
Linux users are strongly advised to update to Shim version 15.8, which not only patches CVE-2023-40547 but also addresses five other significant vulnerabilities.
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