Medium · CVSS 6.4CVE-2026-97876

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

Answer in brief

CVE-2026-97876 records a Medium severity (CVSS 6.4) vulnerability in Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address. The current sources do not mark it as known exploited. The current feed maps GNU/grub2 (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 2, 2026Updated Oct 2, 2026Source checked Oct 2, 2026First seen by HOL Oct 2, 2026Material review Oct 2, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.4
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps GNU/grub2 (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
GNU/grub2generic	>=2.12 <2.16	2.16

Recommended response

Check inventory. Check lockfiles and deployed manifests for GNU/grub2.
Review the reported fix. Update GNU/grub2 to 2.16 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 2, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 2, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 2, 2026

Sources and claim methodology

Upstream source description

A 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.

Quoted source text, attributed separately from HOL analysis.