How severe is CVE-2021-3418?

CVE-2021-3418 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over local access with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3418 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3418?

CVE-2021-3418 affects Gnu Grub2. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3418?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3418 published?

CVE-2021-3418 was published on 2021-03-15 and last updated on 2026-06-17.

CVE-2021-3418

CVE-2021-3418 is a medium-severity vulnerability in Gnu Grub2 with a CVSS 3.x base score of 6.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-281.

Key facts

Severity: Medium (CVSS 3.x base score 6.4)
CVSS v2: 4.4
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-281
Affected product: Gnu Grub2
Published: 2021-03-15
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-3418?: 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.
How severe is CVE-2021-3418?: CVE-2021-3418 has a CVSS 3.x base score of 6.4, rated medium severity. It is exploitable over local access with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3418 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3418?: CVE-2021-3418 affects Gnu Grub2. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3418?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3418 published?: CVE-2021-3418 was published on 2021-03-15 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:gnu:grub2:*:*:*:*:*:*:*:*

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