Vulnerability identifier: #VU51196

Vulnerability risk: Low

CVSSv3.1: 3.6 [CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-3418

CWE-ID: CWE-281

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
grub
Universal components / Libraries / Libraries used by multiple products

Vendor: GNU

Description

The vulnerability allows a local user to bypass implemented security restrictions.

The vulnerability exists doe to re-introduction of vulnerability #VU32927, fixed in GRUB 2.05. If certificates that signed GRUB2 are installed into db, GRUB2 can be booted directly. It will then boot any kernel without signature validation. The booted kernel will think it was booted in Secure Boot mode and will implement lock down, yet it could have been tampered.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

grub: 2.05 - 2.06

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External links
http://seclists.org/oss-sec/2021/q1/189

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.