CVE-2021-21381
Assigner: GitHub_M
Published: 2021-03-11T00:00:00
State: PUBLISHED
title: Sandbox escape via special tokens in .desktop file
descriptions: value: Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the "file forwarding" feature which can be used by an attacker to gain access to files that would not ordinarily be allowed by the app's permissions. By putting the special tokens `@@` and/or `@@u` in the Exec field of a Flatpak app's .desktop file, a malicious app publisher can trick flatpak into behaving as though the user had chosen to open a target file with their Flatpak app, which automatically makes that file available to the Flatpak app. This is fixed in version 1.10.2. A minimal solution is the first commit "`Disallow @@ and @@U usage in desktop files`". The follow-up commits "`dir: Reserve the whole @@ prefix`" and "`dir: Refuse to export .desktop files with suspicious uses of @@ tokens`" are recommended, but not strictly required. As a workaround, avoid installing Flatpak apps from untrusted sources, or check the contents of the exported `.desktop` files in `exports/share/applications/*.desktop` (typically `~/.local/share/flatpak/exports/share/applications/*.desktop` and `/var/lib/flatpak/exports/share/applications/*.desktop`) to make sure that literal filenames do not follow `@@` or `@@u`.
affected: vendor: flatpak
product: flatpak
versions: version: >= 0.9.4, < 1.10.2
status: affected
metrics: cvssV3_1: version: 3.1
vectorString: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
attackVector: LOCAL
attackComplexity: LOW
privilegesRequired: NONE
userInteraction: REQUIRED
scope: CHANGED
confidentialityImpact: LOW
integrityImpact: HIGH
availabilityImpact: NONE
baseScore: 7.1
baseSeverity: HIGH
problemTypes: descriptions: type: CWE
description: CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
cweId: CWE-74
source: advisory: GHSA-xgh4-387p-hqpp
discovery: UNKNOWN