Subject: [ASA-202103-4] flatpak: sandbox escape

Arch Linux Security Advisory ASA-202103-4
=========================================

Severity: Medium
Date    : 2021-03-13
CVE-ID  : CVE-2021-21381
Package : flatpak
Type    : sandbox escape
Remote  : No
Link    : https://security.archlinux.org/AVG-1678

Summary
=======

The package flatpak before version 1.10.2-1 is vulnerable to sandbox
escape.

Resolution
==========

Upgrade to 1.10.2-1.

# pacman -Syu "flatpak>=1.10.2-1"

The problem has been fixed upstream in version 1.10.2.

Workaround
==========

None.

Description
===========

Flatpack since version 0.9.4 and before version 1.10.2 has a
vulnerability in the "file forwarding" feature which can be used by an
attacker to gain access to files that would not ordinarily be allowed
by the app's permissions. By putting the special tokens `@@` and/or
`@@u` in the Exec field of a Flatpak app's .desktop file, a malicious
app publisher can trick flatpak into behaving as though the user had
chosen to open a target file with their Flatpak app, which
automatically makes that file available to the Flatpak app. This is
fixed in version 1.10.2.

Impact
======

A malicious app publisher can escape the sandbox to access sensitive
files.

References
==========

https://github.com/flatpak/flatpak/security/advisories/GHSA-xgh4-387p-hqpp
https://github.com/flatpak/flatpak/issues/4146
https://github.com/flatpak/flatpak/pull/4156
https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d961
https://security.archlinux.org/CVE-2021-21381