Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-97876
StatePUBLISHED
Assignercanonical
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-02 11:17:39 UTC
Updated2026-10-02 18:44:11 UTC
DescriptionA local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.

Risk And Classification

Primary CVSS: v3.1 6.4 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001150000 probability, percentile 0.013770000 (date 2026-10-03)

Problem Types: CWE-822 | CWE-822 CWE-822 Untrusted pointer dereference

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.4MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS6.4MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA GNU Grub2 affected 2.12 2.16 semver Not specified

References

ReferenceSourceLinkTags
gitlab.freedesktop.org/gnu-grub/grub/-/commit/26beaa3b2720fefdc4d04c1ae209b776fe6848d6 [email protected] gitlab.freedesktop.org
www.openwall.com/lists/oss-security/2026/09/13/5 [email protected] www.openwall.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Leïth Essid (en)

CNA: Andrew Hamilton (en)

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