CVE-2021-21261: Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. A bug was discovered in the `flatpak-portal` service that…

PriorityP348high8.8CVSS 3.1

AVLACLPRLUINSCCHIHAH

EPSS

0.57%

42.9th percentile

Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. 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 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 1.10.0.

Affected

10 ranges

Vendor	Product	Version range	Fixed in
debian	debian_linux	—	—
debian	flatpak	< flatpak 1.8.5-1 (bookworm)	flatpak 1.8.5-1 (bookworm)
flatpak	flatpak	—	—
flatpak	flatpak	—	—
flatpak	flatpak	>= 0 < 1.8.5-1	1.8.5-1
flatpak	flatpak	>= 0 < 1.8.5-1	1.8.5-1
flatpak	flatpak	>= 0 < 1.8.5-1	1.8.5-1
flatpak	flatpak	>= 0 < 1.8.5-1	1.8.5-1
flatpak	flatpak	>= 0.11.4 < 1.8.5	1.8.5
flatpak	flatpak	>= 1.9.1 < 1.10.0	1.10.0

CVSS provenance

nvdv3.18.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

nvdv2.07.2HIGHAV:L/AC:L/Au:N/C:C/I:C/A:C

osv8.8HIGH

vendor_debian7.3HIGH

vendor_redhat7.3HIGH

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