February 7, 2024 at 05:23PM
Major Linux distros, including Red Hat, Ubuntu, Debian, and SUSE, are affected by a remote code execution vulnerability in Linux shim (CVE-2023-40547). The flaw allows attackers to take full control of affected systems during the secure boot process. Red Hat has issued an update to address the most severe of six vulnerabilities in Linux shim. Different severity ratings have been assigned to the vulnerability, and it can be exploited through multiple attack vectors, but some security experts believe its severity has been exaggerated.
Based on the meeting notes, the key takeaways are as follows:
1. Linux shim, used during the secure boot process, has a critical remote code execution vulnerability (CVE-2023-40547) that affects all Linux distributions supporting Secure Boot.
2. Red Hat has released an update (shim 15.8) to address the vulnerability, which was disclosed by researcher Bill Demirkapi and allows for complete system compromise through an out-of-bounds write error.
3. The severity of the vulnerability is the subject of differing assessments from the National Vulnerability Database (NVD) and Red Hat, with NVD providing a higher severity rating than Red Hat. Red Hat attributes the difference to vendor-specific factors.
4. The vulnerability affects the shim bootloader, which verifies the main OS bootloader before loading and running it, and has been identified as having multiple attack vectors including man-in-the-middle attacks and local exploitation.
5. While some security experts perceive the vulnerability as requiring a high degree of complexity to exploit, others argue that it presents serious concerns for machines using HTTP boot or pre-boot execution environment (PXE) boot.
6. There is disagreement regarding the severity of the vulnerability, with some experts suggesting that the NVD’s assessment may be overstating the risk by assuming an unlikely worst-case scenario.
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