CVE-2021-3418

Severity: medium (CVSS 6.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-15 · updated 2026-06-17
Weakness: CWE-281

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.

Affected products

grub2: before 2.06 — fixed in 2.06

How to fix

Upgrade to a fixed version: grub2 2.06. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=1933757
https://bugzilla.redhat.com/show_bug.cgi?id=1933757

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