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CVE-2020-15706

Published: 29 July 2020

GRUB2 contains a race condition in grub_script_function_create() leading to a use-after-free vulnerability which can be triggered by redefining a function whilst the same function is already executing, leading to arbitrary code execution and secure boot restriction bypass. This issue affects GRUB2 version 2.04 and prior versions.

From the Ubuntu Security Team

Chris Coulson discovered that the GRUB2 function handling code did not properly handle a function being redefined, leading to a use-after-free vulnerability. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions.

Notes

AuthorNote
alexmurray
grub2-signed is not supported in Ubuntu 12.04 ESM (precise/esm) and so marking the priority for grub2 in this release as low
sbeattie
809f3a268 script: Avoid a use-after-free when redefining a function during execution

Priority

High

Cvss 3 Severity Score

6.4

Score breakdown

Status

Package Release Status
grub2
Launchpad, Ubuntu, Debian
jammy Not vulnerable
(2.06-2ubuntu7)
kinetic Not vulnerable
(2.06-2ubuntu12)
lunar Not vulnerable
(2.06-2ubuntu16)
hirsute Not vulnerable
(2.04-1ubuntu26.1)
bionic
Released (2.02-2ubuntu8.16)
focal
Released (2.04-1ubuntu26.1)
groovy Not vulnerable
(2.04-1ubuntu26.1)
trusty
Released (2.02~beta2-9ubuntu1.20)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only)
upstream Needs triage

xenial
Released (2.02~beta2-36ubuntu3.26)
mantic Not vulnerable
(2.06-2ubuntu18)
grub2-signed
Launchpad, Ubuntu, Debian
jammy Not vulnerable
(1.180)
kinetic Not vulnerable
(1.185)
lunar Not vulnerable
(1.192)
hirsute Not vulnerable
(1.147)
bionic
Released (1.93.18)
focal
Released (1.142.3)
groovy Not vulnerable
(1.147)
trusty
Released (1.34.22)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only)
upstream Needs triage

xenial
Released (1.66.26)
mantic Not vulnerable
(1.193)
grub2-unsigned
Launchpad, Ubuntu, Debian
trusty Does not exist

xenial Needed

bionic Not vulnerable
(2.04-1ubuntu47.4)
focal Not vulnerable
(2.04-1ubuntu47.4)
jammy Not vulnerable
(2.06-2ubuntu10)
kinetic Not vulnerable
(2.06-2ubuntu12)
lunar Not vulnerable
(2.06-2ubuntu16)
upstream Needs triage

mantic Not vulnerable
(2.06-2ubuntu17)

Severity score breakdown

Parameter Value
Base score 6.4
Attack vector Local
Attack complexity High
Privileges required High
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H