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CVE-2021-21261

CVE-2021-21261 · Flatpak sandbox escape via spawn portal

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 7.3 · High · EPSS 0.6% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • flatpak

    Versions
    • >= 0.11.4, < 1.8.5: Affected
    • >= 1.9.0, < 1.10.0: Affected

    No fix published

  • flatpak Debian:12

    Affected ranges
    • ECOSYSTEM: < 1.8.5-1

    Update to 1.8.5-1

  • flatpak Debian:13

    Affected ranges
    • ECOSYSTEM: < 1.8.5-1

    Update to 1.8.5-1

  • flatpak Debian:14

    Affected ranges
    • ECOSYSTEM: < 1.8.5-1

    Update to 1.8.5-1

  • flatpak Ubuntu:18.04:LTS

    Versions
    • 0.8.7-5
    • 0.10.0-1
    • 0.10.0-2
    • 0.10.1-1
    • 0.10.2-1
    • 0.10.2.1-1
    • 0.10.2.1-2
    • 0.10.3-1
    • 0.11.1-0ubuntu1
    • 0.11.3-2
    • 0.11.3-3
    • 0.11.7-0ubuntu0.1
    • 1.0.1-0ubuntu0.1
    • 1.0.6-0ubuntu0.1
    • 1.0.7-0ubuntu0.18.04.1
    • 1.0.8-0ubuntu0.18.04.1
    • 1.0.9-0ubuntu0.1
    Affected ranges
    • ECOSYSTEM: < 1.0.9-0ubuntu0.2

    Update to 1.0.9-0ubuntu0.2

  • flatpak Ubuntu:20.04:LTS

    Versions
    • 1.4.3-1
    • 1.6.0-1
    • 1.6.1-1
    • 1.6.2-1
    • 1.6.3-1
    • 1.6.5-0ubuntu0.1
    Affected ranges
    • ECOSYSTEM: < 1.6.5-0ubuntu0.2

    Update to 1.6.5-0ubuntu0.2

Original sources

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