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CVE-2021-20233

Publication date 2 March 2021

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

8.2 · High

Score breakdown

A flaw was found in grub2 in versions prior to 2.06. Setparam_prefix() in the menu rendering code performs a length calculation on the assumption that expressing a quoted single quote will require 3 characters, while it actually requires 4 characters which allows an attacker to corrupt memory by one byte for each quote in the input. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

From the Ubuntu Security Team

It was discovered that the menu rendering implementation in GRUB 2 did not properly calculate the amount of memory needed in some situations, leading to out-of-bounds writes. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions.

Read the notes from the security team

Status

Package Ubuntu Release Status
grub2 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
grub2-signed 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Fixed 1.169
21.04 hirsute
Fixed 1.164
20.10 groovy
Fixed 1.167.2
20.04 LTS focal
Fixed 1.167.2
18.04 LTS bionic
Fixed 1.167~18.04.5
16.04 LTS xenial
Fixed 1.164
14.04 LTS trusty
Vulnerable
grub2-unsigned 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Fixed 2.04-1ubuntu45
21.04 hirsute
Fixed 2.04-1ubuntu42
20.10 groovy
Fixed 2.04-1ubuntu44.2
20.04 LTS focal
Fixed 2.04-1ubuntu44.2
18.04 LTS bionic
Fixed 2.04-1ubuntu44.1.2
16.04 LTS xenial
Fixed 2.04-1ubuntu42
14.04 LTS trusty Not in release

Notes

sbeattie

grub2-unsigned will contain fixes and supersede grub2, which will contain only BIOS grub bits.

Severity score breakdown

Parameter Value
Base score 8.2 · High
Attack vector Local
Attack complexity Low
Privileges required High
User interaction None
Scope Changed
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

Other references