CVE-2021-20233
Publication date 2 March 2021
Last updated 24 July 2024
Ubuntu priority
Cvss 3 Severity Score
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.
Status
Package | Ubuntu Release | Status |
---|---|---|
grub2 | 24.04 LTS noble |
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 | 24.04 LTS noble |
Not affected
|
22.04 LTS jammy |
Not affected
|
|
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 | 24.04 LTS noble |
Not affected
|
22.04 LTS jammy |
Not affected
|
|
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)
- USN-4992-1
- GRUB 2 vulnerabilities
- 18 June 2021