A firejail security update has been released for Arch Linux.

ASA-202102-26: firejail: privilege escalation

Arch Linux Security Advisory ASA-202102-26
=========================================
Severity: High
Date : 2021-02-12
CVE-ID : CVE-2021-26910
Package : firejail
Type : privilege escalation
Remote : No
Link :   https://security.archlinux.org/AVG-1545

Summary
======
The package firejail before version 0.9.64.4-1 is vulnerable to
privilege escalation.

Resolution
=========
Upgrade to 0.9.64.4-1.

# pacman -Syu "firejail>=0.9.64.4-1"

The problem has been fixed upstream in version 0.9.64.4.

Workaround
=========
The issue can be mitigated by setting "overlayfs no" in
/etc/firejail/firejail.config.

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.

Impact
=====
A local unprivileged attacker can obtain arbitrary file system access
for an application running within a firejail sandbox, leading to
potential privilege escalation.

References
=========
  https://unparalleled.eu/publications/2021/advisory-unpar-2021-0.txt
  https://unparalleled.eu/blog/2021/20210208-rigged-race-against-firejail-for-local-root/
  https://github.com/netblue30/firejail/commit/97d8a03cad19501f017587cc4e47d8418273834b
  https://security.archlinux.org/CVE-2021-26910