Skip to content
Fencer Vulns
high 8.8

CVE-2021-41133 json

Sandbox bypass via recent VFS-manipulating syscalls

published 2021-10-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-28254

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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.

Patch / fix

  • flatpak flatpak 1.8.2, 1.12.0
  • flatpak Debian 14, Debian 13, Debian 12 1.12.1-1

debian advisories DEBIAN-CVE-2021-41133

  • flatpak Ubuntu 18.04 LTS 1.0.9-0ubuntu0.4
  • flatpak Ubuntu 20.04 LTS 1.6.5-0ubuntu0.4

ubuntu advisories UBUNTU-CVE-2021-41133

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • flatpak RHEL 7 1.0.9-12.el7_9
  • flatpak-libs RHEL 7 1.0.9-12.el7_9
  • flatpak-builder RHEL 7 1.0.0-12.el7_9
  • flatpak RHEL 8 1.8.5-4.el8_4
  • flatpak-libs RHEL 8 1.8.5-4.el8_4
  • flatpak-selinux RHEL 8 1.8.5-4.el8_4
  • flatpak-session-helper RHEL 8 1.8.5-4.el8_4
  • flatpak RHEL 8.2 EUS 1.6.2-6.el8_2

red hat advisories RHSA-2021:4107RHSA-2021:4106RHSA-2021:4044RHSA-2021:4042

  • flatpak SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 0.10.4-150000.4.13.1
  • flatpak SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +3 more 1.2.3-150100.4.8.1
  • flatpak SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 1.10.5-4.9.1

suse advisories SUSE-SU-2022:3439-1SUSE-SU-2022:3284-1SUSE-SU-2021:3472-1

  • flatpak openSUSE Tumbleweed 1.12.1-1.1
  • flatpak openSUSE Leap 15.2 1.10.5-lp152.3.9.1
  • flatpak openSUSE Leap 15.3 1.10.5-4.9.1

opensuse advisories openSUSE-SU-2024:11574-1openSUSE-SU-2021:1400-1openSUSE-SU-2021:3472-1

  • flatpak AlmaLinux 8 1.8.5-5.el8_5
  • flatpak-libs AlmaLinux 8 1.8.5-5.el8_5
  • flatpak-selinux AlmaLinux 8 1.8.5-5.el8_5
  • flatpak-session-helper AlmaLinux 8 1.8.5-5.el8_5
  • flatpak AlmaLinux 8 1.8.5-4.el8_4
  • flatpak-libs AlmaLinux 8 1.8.5-4.el8_4
  • flatpak-selinux AlmaLinux 8 1.8.5-4.el8_4
  • flatpak-session-helper AlmaLinux 8 1.8.5-4.el8_4

almalinux advisories ALEA-2021:4539ALSA-2021:4042

  • flatpak Rocky Linux 8 1.8.5-4.el8_4
  • flatpak Rocky Linux 8 1.8.5-4.el8

rocky linux advisories RLSA-2021:4042

  • flatpak Alpine 3.14 1.10.5-r0
  • flatpak Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 1.12.2-r0

alpine advisories ALPINE-CVE-2021-41133

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • flatpak Arch Linux 1.12.0-1

arch linux advisories AVG-2455

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-41133 updated cvss 8.8

flatpak: Sandbox bypass via recent VFS-manipulating syscalls

  • Red Hat Enterprise Linux AppStream (v. 8) flatpak 1.8.5-4.el8_4, flatpak-libs 1.8.5-4.el8_4, flatpak-selinux 1.8.5-4.el8_4, flatpak-session-helper 1.8.5-4.el8_4
    fixed: vendor fix RHSA-2021:4042
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) flatpak 1.0.9-5.el8_1, flatpak-libs 1.0.9-5.el8_1
    fixed: vendor fix RHSA-2021:4106
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) flatpak 1.6.2-6.el8_2, flatpak-libs 1.6.2-6.el8_2, flatpak-selinux 1.6.2-6.el8_2, flatpak-session-helper 1.6.2-6.el8_2
    fixed: vendor fix RHSA-2021:4107
  • Red Hat Enterprise Linux Client (v. 7) flatpak 1.0.9-12.el7_9, flatpak-libs 1.0.9-12.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) flatpak-builder 1.0.0-12.el7_9 Red Hat Enterprise Linux ComputeNode Optional (v. 7) flatpak 1.0.9-12.el7_9, flatpak-libs 1.0.9-12.el7_9, flatpak-builder 1.0.0-12.el7_9 Red Hat Enterprise Linux Server (v. 7) flatpak 1.0.9-12.el7_9, flatpak-libs 1.0.9-12.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) flatpak-builder 1.0.0-12.el7_9 Red Hat Enterprise Linux Workstation (v. 7) flatpak 1.0.9-12.el7_9, flatpak-libs 1.0.9-12.el7_9
    +1 more products
    Red Hat Enterprise Linux Workstation Optional (v. 7) flatpak-builder 1.0.0-12.el7_9
    fixed: vendor fix RHSA-2021:4044
  • Red Hat Enterprise Linux 9 flatpak, flatpak-libs, flatpak-selinux, flatpak-session-helper
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • flatpak flatpak
  • fedoraproject fedora
  • debian debian_linux

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.