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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.

Priority

Medium

CVSS 3 base score: 7.5

Status

Package Release Status
grub2-signed
Launchpad, Ubuntu, Debian
bionic
Released (1.167~18.04.5)
focal
Released (1.167.2)
groovy
Released (1.167.2)
hirsute
Released (1.164)
impish
Released (1.169)
jammy
Released (1.169)
precise Does not exist

trusty Needs triage

upstream Needs triage

xenial Pending
(1.164)
grub2-unsigned
Launchpad, Ubuntu, Debian
bionic
Released (2.04-1ubuntu44.1.2)
focal
Released (2.04-1ubuntu44.2)
groovy
Released (2.04-1ubuntu44.2)
hirsute
Released (2.04-1ubuntu42)
impish
Released (2.04-1ubuntu45)
jammy
Released (2.04-1ubuntu45)
precise Ignored
(end of ESM support, was needs-triage)
trusty Needs triage

upstream Needs triage

xenial Pending
(2.04-1ubuntu42)

Notes

AuthorNote
amurray
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.

References

Bugs