CVE-2021-43540

Publication date 8 December 2021

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party websites that would not have been uninstalled with the extension. This vulnerability affects Firefox < 95.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
firefox	23.04 lunar	Fixed 95.0+build1-0ubuntu1
	22.10 kinetic	Fixed 95.0+build1-0ubuntu1
	22.04 LTS jammy	Fixed 95.0+build1-0ubuntu1
	21.10 impish	Fixed 95.0+build1-0ubuntu0.21.10.1
	21.04 hirsute	Fixed 95.0+build1-0ubuntu0.21.04.1
	20.04 LTS focal	Fixed 95.0+build1-0ubuntu0.20.04.1
	18.04 LTS bionic	Fixed 95.0+build1-0ubuntu0.18.04.1
	16.04 LTS xenial	Ignored end of standard support, was needed
	14.04 LTS trusty	Not in release

Notes

tyhicks

mozjs contains a copy of the SpiderMonkey JavaScript engine

Severity score breakdown

Parameter	Value
Base score	6.5 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality	None
Integrity impact	High
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

References

Related Ubuntu Security Notices (USN)

USN-5186-1
Firefox vulnerabilities
9 December 2021