CVE-2021-41133
Assigner: GitHub_M
Published: 2021-10-08T00:00:00
State: PUBLISHED
title: Sandbox bypass via recent VFS-manipulating syscalls
descriptions: value: Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In versions prior to 1.10.4 and 1.12.0, Flatpak apps with direct access to AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can trick portals and other host-OS services into treating the Flatpak app as though it was an ordinary, non-sandboxed host-OS process. They can do this by manipulating the VFS using recent mount-related syscalls that are not blocked by Flatpak's denylist seccomp filter, in order to substitute a crafted `/.flatpak-info` or make that file disappear entirely. Flatpak apps that act as clients for AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can escalate the privileges that the corresponding services will believe the Flatpak app has. Note that protocols that operate entirely over the D-Bus session bus (user bus), system bus or accessibility bus are not affected by this. This is due to the use of a proxy process `xdg-dbus-proxy`, whose VFS cannot be manipulated by the Flatpak app, when interacting with these buses. Patches exist for versions 1.10.4 and 1.12.0, and as of time of publication, a patch for version 1.8.2 is being planned. There are no workarounds aside from upgrading to a patched version.
affected: vendor: flatpak
product: flatpak
versions: version: >= 1.8.0, <= 1.8.2
status: affected
version: >= 1.10.0, < 1.10.4
status: affected
version: >= 1.11.0, < 1.12.0
status: affected
metrics: cvssV3_1: version: 3.1
vectorString: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
attackVector: LOCAL
attackComplexity: LOW
privilegesRequired: LOW
userInteraction: NONE
scope: CHANGED
confidentialityImpact: HIGH
integrityImpact: HIGH
availabilityImpact: HIGH
baseScore: 8.8
baseSeverity: HIGH
problemTypes: descriptions: type: CWE
description: CWE-20: Improper Input Validation
cweId: CWE-20
source: advisory: GHSA-67h7-w3jq-vh4q
discovery: UNKNOWN