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Fencer Intel
medium 6.4

CVE-2026-97876 json

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

published last mo. modified last mo. also EUVD-2026-91376

cvss
6.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

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.

Patch / fix

  • GNU grub2 2.16
  • grub2 Debian 14 2.14-4

debian advisories DEBIAN-CVE-2026-97876

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-97876 updated cvss 6.4

grub2: grub2: Secure Boot lockdown bypass via improper serial address validation

  • Red Hat Enterprise Linux 7 grub2, grub2-pc, grub2-efi, grub2-ppc64, grub2-tools, grub2-common, +16 more Red Hat Enterprise Linux 8 grub2-pc, grub2-tools, grub2-common, grub2-efi-x64, grub2-ppc64le, grub2-efi-aa64, +13 more Red Hat Enterprise Linux 9 grub2-pc, grub2-tools, grub2-common, grub2-efi-x64, grub2-ppc64le, grub2-efi-aa64, +10 more Red Hat Enterprise Linux 10 grub2 2.12-46.el10_2 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
last mo.

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 6.4 CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected products

  • GNU grub2

Classification

Weakness
  • CWE-822 Untrusted Pointer Dereference

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.