CVE-2021-26318

Publication date 13 October 2021

Last updated 21 January 2026

Ubuntu priority

Cvss 3 Severity Score

Description

A timing and power-based side channel attack leveraging the x86 PREFETCH instructions on some AMD CPUs could potentially result in leaked kernel address space information.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
amd64-microcode	25.10 questing	Not affected
	25.04 plucky	Ignored end of life, was deferred
	24.10 oracular	Ignored end of life, was deferred
	24.04 LTS noble	Not affected
	23.10 mantic	Ignored end of life, was deferred
	23.04 lunar	Ignored end of life, was deferred
	22.10 kinetic	Ignored end of life, was deferred
	22.04 LTS jammy	Not affected
	21.10 impish	Ignored end of life
	21.04 hirsute	Ignored end of life
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

rodrigo-zaiden

AMD provides recommendation of best practices as mitigation to this issue and there is no microcode updates for it.

Severity score breakdown

Parameter	Value
Base score	4.7 · Medium
Attack vector	Local
Attack complexity	High
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	None
Availability impact	None
Vector	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N