CVE-2021-29951

Publication date 24 June 2021

Last updated 1 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

The Mozilla Maintenance Service granted SERVICE_START access to BUILTIN|Users which, in a domain network, grants normal remote users access to start or stop the service. This could be used to prevent the browser update service from operating (if an attacker spammed the 'Stop' command); but also exposed attack surface in the maintenance service. *Note: This issue only affected Windows operating systems older than Win 10 build 1709. Other operating systems are unaffected.*. This vulnerability affects Thunderbird < 78.10.1, Firefox < 87, and Firefox ESR < 78.10.1.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
firefox	21.04 hirsute	Not affected
	20.10 groovy	Not affected
	20.04 LTS focal	Not in release
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Ignored end of standard support
	14.04 LTS trusty	Not in release
firefox-esr	21.04 hirsute	Not in release
	20.10 groovy	Not in release
	20.04 LTS focal	Not in release
	18.04 LTS bionic	Not in release
	16.04 LTS xenial	Ignored end of standard support
	14.04 LTS trusty	Not in release
thunderbird	21.04 hirsute	Not affected
	20.10 groovy	Not affected
	20.04 LTS focal	Not in release
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Ignored end of standard support
	14.04 LTS trusty	Not in release

Notes

alexmurray

Only affects Firefox on Windows, does not affect Firefox on Ubuntu

Severity score breakdown

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