Grub2
CVE-2021-3418
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Permission preservation
|
| Impact | CVSS score of 6.4 (MEDIUM). Attack characteristics: local attack vector, high complexity, high privileges required, no user interaction not required. |
| Exploit ScenarioDerived | Successful exploitation could compromise the medium-severity affected system. |
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Alert meAnalysisAI
If certificates that signed grub are installed into db, grub can be booted directly. Rated medium severity (CVSS 6.4). No vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
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Technical ContextAI · show details
This vulnerability is classified under CWE-281. 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 include: Gnu Grub2. Version information: prior to 2.06.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
Affected Products (CPE)NVD
Multiple integer underflows in Grub2 1.98 through 2.02 allow physically proximate attackers to bypass authentication, ob
An out-of-bounds write flaw was found in grub2's NTFS filesystem driver. Rated high severity (CVSS 7.8), this vulnerabil
GRUB2 does not call the module fini functions on exit, leading to Debian/Ubuntu's peimage GRUB2 module leaving UEFI syst
Integer overflows were discovered in the functions grub_cmd_initrd and grub_initrd_init in the efilinux component of GRU
GNU GRUB (aka GRUB2) through 2.12 has a heap-based buffer overflow in fs/hfs.c via crafted sblock data in an HFS filesys
An out-of-bounds read flaw was found on grub2's NTFS filesystem driver. Rated medium severity (CVSS 4.6), this vulnerabi
A buffer overflow was found in grub_font_construct_glyph(). Rated high severity (CVSS 8.6), this vulnerability is no aut
A flaw was found in grub2 in versions prior to 2.06. Rated high severity (CVSS 8.2), this vulnerability is low attack co
A flaw was found in grub2, prior to version 2.06. Rated high severity (CVSS 8.2), this vulnerability is low attack compl
A flaw was found in grub2. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch
A flaw was found in the HFS filesystem. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No
When reading data from a hfs filesystem, grub's hfs filesystem module uses user-controlled parameters from the filesyste
GitHub PoC
Exploit-DB