Arch Linux Security Advisory ASA-202101-40

Severity: High
Date    : 2021-01-20
CVE-ID  : CVE-2021-21261
Package : flatpak
Type    : sandbox escape
Remote  : No
Link    :


The package flatpak before version 1.10.0-1 is vulnerable to sandbox


Upgrade to 1.10.0-1.

# pacman -Syu "flatpak>=1.10.0-1"

The problem has been fixed upstream in version 1.10.0.




A bug was discovered in the `flatpak-portal` service that can allow
sandboxed applications to execute arbitrary code on the host system (a
sandbox escape). This sandbox-escape bug is present in versions from
0.11.4 and before the fixed versions 1.8.5 and 1.10.0. The Flatpak
portal D-Bus service (`flatpak-portal`, also known by its D-Bus service
name `org.freedesktop.portal.Flatpak`) allows apps in a Flatpak sandbox
to launch their own subprocesses in a new sandbox instance, either with
the same security settings as the caller or with more restrictive
security settings. For example, this is used in Flatpak-packaged web
browsers such as Chromium to launch subprocesses that will process
untrusted web content, and give those subprocesses a more restrictive
sandbox than the browser itself. In vulnerable versions, the Flatpak
portal service passes caller-specified environment variables to non-
sandboxed processes on the host system, and in particular to the
`flatpak run` command that is used to launch the new sandbox instance.
A malicious or compromised Flatpak app could set environment variables
that are trusted by the `flatpak run` command, and use them to execute
arbitrary code that is not in a sandbox. As a workaround, this
vulnerability can be mitigated by preventing the `flatpak-portal`
service from starting, but that mitigation will prevent many Flatpak
apps from working correctly. This is fixed in versions 1.8.5 and


A malicious application could execute arbitrary code on the host.