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CVE-2020-14372

Published: 2 March 2021

A flaw was found in grub2 in versions prior to 2.06, where it incorrectly enables the usage of the ACPI command when Secure Boot is enabled. This flaw allows an attacker with privileged access to craft a Secondary System Description Table (SSDT) containing code to overwrite the Linux kernel lockdown variable content directly into memory. The table is further loaded and executed by the kernel, defeating its Secure Boot lockdown and allowing the attacker to load unsigned code. The highest threat from this vulnerability is to data confidentiality and integrity, as well as system availability.

From the Ubuntu Security Team

Máté Kukri discovered that the acpi command in GRUB 2 allowed privileged users to load crafted ACPI tables when secure boot is enabled. An attacker could use this to bypass UEFI Secure Boot restrictions.

Notes

AuthorNote
alexmurray
CVE title: "grub2: acpi command allows privileged user to load crafted ACPI tables when secure boot is enabled"
sbeattie
grub2-unsigned will contain fixes and supersede grub2, which will contain only BIOS grub bits.

Priority

Medium

Cvss 3 Severity Score

7.5

Score breakdown

Status

Package Release Status
grub2-unsigned
Launchpad, Ubuntu, Debian
impish
Released (2.04-1ubuntu45)
jammy Not vulnerable
(2.06-2ubuntu7)
kinetic Not vulnerable
(2.06-2ubuntu12)
lunar Not vulnerable
(2.06-2ubuntu16)
bionic
Released (2.04-1ubuntu44.1.2)
focal
Released (2.04-1ubuntu44.2)
groovy
Released (2.04-1ubuntu44.2)
hirsute
Released (2.04-1ubuntu42)
trusty Does not exist

upstream Needs triage

xenial Pending
(2.04-1ubuntu42)
grub2-signed
Launchpad, Ubuntu, Debian
impish
Released (1.169)
upstream Needs triage

trusty Needed

hirsute
Released (1.164)
bionic
Released (1.167~18.04.5)
focal
Released (1.167.2)
xenial Pending
(1.164)
groovy
Released (1.167.2)
jammy Not vulnerable
(1.180)
kinetic Not vulnerable
(1.185)
lunar Not vulnerable
(1.192)
grub2
Launchpad, Ubuntu, Debian
trusty Needed

xenial Needed

bionic Needed

focal Needed

jammy Not vulnerable
(2.06-2ubuntu7)
kinetic Not vulnerable
(2.06-2ubuntu12)
lunar Not vulnerable
(2.06-2ubuntu16)
upstream Needs triage

Severity score breakdown

Parameter Value
Base score 7.5
Attack vector Local
Attack complexity High
Privileges required High
User interaction None
Scope Changed
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H