Debian Security Advisory

DSA-4830-1 flatpak -- security update

Date Reported:
14 Jan 2021
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2021-21261.
More information:

Simon McVittie discovered a bug in the flatpak-portal service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape).

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.

For the stable distribution (buster), this problem has been fixed in version 1.2.5-0+deb10u2.

We recommend that you upgrade your flatpak packages.

For the detailed security status of flatpak please refer to its security tracker page at: