Vulnerability · Published Oct 2, 2026 · Assigned by canonical
CVE-2026-97876Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address
Medium 6.4
In plain English
A medium-severity security flaw in grub2 from GNU. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | grub2 | no fix listed | DEBIAN-CVE-2026-97876 |
| Debian:14 | grub2 | 2.14-4 | DEBIAN-CVE-2026-97876 |
| Ubuntu:22.04:LTS | grub2-signed | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:24.04:LTS | grub2-signed | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:26.04:LTS | grub2-signed | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:26.10 | grub2-signed | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:22.04:LTS | grub2-unsigned | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:24.04:LTS | grub2-unsigned | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:26.04:LTS | grub2-unsigned | no fix listed | UBUNTU-CVE-2026-97876 |
| Ubuntu:26.10 | grub2-unsigned | no fix listed | UBUNTU-CVE-2026-97876 |
Affected products (as reported)
Weakness: CWE-822 · Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H