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CVE-2021-41133

CVE-2021-41133 · Sandbox bypass via recent VFS-manipulating syscalls

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. 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.

CVSS 8.8 · High · EPSS 0.4% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • flatpak

    Versions
    • >= 1.8.0, <= 1.8.2: Affected
    • >= 1.10.0, < 1.10.4: Affected
    • >= 1.11.0, < 1.12.0: Affected

    No fix published

  • flatpak Debian:12

    Affected ranges
    • ECOSYSTEM: < 1.12.1-1

    Update to 1.12.1-1

  • flatpak Debian:13

    Affected ranges
    • ECOSYSTEM: < 1.12.1-1

    Update to 1.12.1-1

  • flatpak Debian:14

    Affected ranges
    • ECOSYSTEM: < 1.12.1-1

    Update to 1.12.1-1

  • 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
    • 1.0.9-0ubuntu0.2
    • 1.0.9-0ubuntu0.3
    Affected ranges
    • ECOSYSTEM: < 1.0.9-0ubuntu0.4

    Update to 1.0.9-0ubuntu0.4

  • 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
    • 1.6.5-0ubuntu0.2
    • 1.6.5-0ubuntu0.3
    Affected ranges
    • ECOSYSTEM: < 1.6.5-0ubuntu0.4

    Update to 1.6.5-0ubuntu0.4

Original sources

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