CVE-2021-3995

Publication date 1 February 2022

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows an unprivileged local attacker to unmount FUSE filesystems that belong to certain other users who have a UID that is a prefix of the UID of the attacker in its string form. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
util-linux	22.04 LTS jammy	Fixed 2.37.2-4ubuntu2
	21.10 impish	Fixed 2.36.1-8ubuntu2.2
	20.04 LTS focal	Fixed 2.34-0.1ubuntu9.3
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

sbeattie

introduced in 5fea669e9ef0a08804f72bb40f859f239f68c30a (v2.34)

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
util-linux	Upstream: 9c05f4b Upstream: 57202f5

Severity score breakdown

Parameter	Value
Base score	5.5 · Medium
Attack vector	Local
Attack complexity	Low
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

USN-5279-1
util-linux vulnerabilities
9 February 2022