CVE-2021-26910

Publication date 8 February 2021

Last updated 26 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

Firejail before 0.9.64.4 allows attackers to bypass intended access restrictions because there is a TOCTOU race condition between a stat operation and an OverlayFS mount operation.

From the Ubuntu Security Team

Roman Fiedler discovered that a race condition existed in Firejail when using OverlayFS to prevent writes to the underlying file system. A local attacker could use this to gain administrative privileges. Note: this update disables support for OverlayFS in Firejail.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
firejail	25.10 questing	Not affected
	25.04 plucky	Not affected
	24.10 oracular	Not affected
	24.04 LTS noble	Not affected
	23.10 mantic	Not affected
	23.04 lunar	Not affected
	22.10 kinetic	Not affected
	22.04 LTS jammy	Not affected
	21.10 impish	Not affected
	21.04 hirsute	Not affected
	20.10 groovy	Ignored end of life
	20.04 LTS focal	Fixed 0.9.62-3ubuntu0.1
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation
	14.04 LTS trusty	Not in release

Severity score breakdown

Parameter	Value
Base score	7.8 · High
Attack vector	Local
Attack complexity	Low
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	High
Integrity impact	High
Availability impact	High
Vector	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

USN-5141-1
Firejail vulnerability
11 November 2021