CVE-2021-41133: Debian Linux

High severity, CVSS 7.8. EPSS: 0.4% chance of exploitation in the next 30 days.

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 products

• Debian Debian Linux: version 11.0 only
• Fedoraproject Fedora: version 33 only; version 34 only
• Flatpak Flatpak: before 1.8.2 (fixed in 1.8.2); from 1.10.0, before 1.10.4 (fixed in 1.10.4); from 1.11.1, before 1.12.1 (fixed in 1.12.1)

Published 2021-10-08. Last modified 2026-06-17.