CVE-2021-3418: gnu grub2 Improper Preservation of Permissions

Vulnerability summary

CVE-2021-3418 is a medium (CVSS 6.4) Improper Preservation of Permissions vulnerability in gnu grub2. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 38.9% of scored vulnerabilities.

Timeline

1. 15-03-2021
   PublishedVulnerability first disclosed.
2. 03-08-2024
   Last modifiedVulnerability information updated.

Description

If certificates that signed grub are installed into db, grub can be booted directly. It will then boot any kernel without signature validation. The booted kernel will think it was booted in secureboot mode and will implement lockdown, yet it could have been tampered. This flaw is a reintroduction of CVE-2020-15705 and only affects grub2 versions prior to 2.06 and upstream and distributions using the shim_lock mechanism.

• CWE-281Improper Preservation of PermissionsThe product does not preserve permissions or incorrectly preserves permissions when copying, restoring, or sharing objects, which can cause them to have less restrictive permissions than intended.