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.
Published 2021-01-14 20:15:12
Updated 2021-01-27 19:34:12
Source GitHub, Inc.
View at NVD,   CVE.org
Vulnerability category: Execute code

Exploit prediction scoring system (EPSS) score for CVE-2021-21261

Probability of exploitation activity in the next 30 days: 0.05%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 20 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2021-21261

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
7.2
HIGH AV:L/AC:L/Au:N/C:C/I:C/A:C
3.9
10.0
NIST
8.8
HIGH CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
2.0
6.0
NIST
7.3
HIGH CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
2.0
4.7
GitHub, Inc.

CWE ids for CVE-2021-21261

References for CVE-2021-21261

Products affected by CVE-2021-21261

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