CVE-2021-21261 Information

Description

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.

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Reference

https://github.com/flatpak/flatpak/releases/tag/1.8.5 https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2 https://www.debian.org/security/2021/dsa-4830 https://github.com/flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba https://github.com/flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486 https://github.com/flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4 https://github.com/flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b https://security.gentoo.org/glsa/202101-21

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

CHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.8