Bug 2012245 (CVE-2021-41133) - CVE-2021-41133 flatpak: Sandbox bypass via recent VFS-manipulating syscalls
Summary: CVE-2021-41133 flatpak: Sandbox bypass via recent VFS-manipulating syscalls
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-41133
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2012246 2012862 2012864 2012865 2012866 2012867 2012868 2012869
Blocks: 2012248
TreeView+ depends on / blocked
 
Reported: 2021-10-08 16:19 UTC by Guilherme de Almeida Suckevicz
Modified: 2022-05-17 09:42 UTC (History)
4 users (show)

Fixed In Version: flatpak 1.12.1
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the flatpak package. It is susceptible to a software flaw that can deceive portals and other host-OS services into treating the flatpak app as an ordinary, non-sandboxed host-OS process. This flaw allows the escalation of privileges that the corresponding services presume the flatpak app has. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Clone Of:
Environment:
Last Closed: 2021-11-01 14:07:50 UTC


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:4042 0 None None None 2021-11-01 13:35:46 UTC
Red Hat Product Errata RHSA-2021:4044 0 None None None 2021-11-01 16:32:53 UTC
Red Hat Product Errata RHSA-2021:4106 0 None None None 2021-11-02 18:22:53 UTC
Red Hat Product Errata RHSA-2021:4107 0 None None None 2021-11-02 20:10:05 UTC

Description Guilherme de Almeida Suckevicz 2021-10-08 16:19:32 UTC
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.

Reference:
https://github.com/flatpak/flatpak/security/advisories/GHSA-67h7-w3jq-vh4q

Comment 1 Guilherme de Almeida Suckevicz 2021-10-08 16:19:47 UTC
Created flatpak tracking bugs for this issue:

Affects: fedora-all [bug 2012246]

Comment 4 devthomp 2021-10-11 14:24:36 UTC
As per link:
https://github.com/flatpak/flatpak/security/advisories/GHSA-67h7-w3jq-vh4q

Patches
The short-term solution is to expand the deny-list of syscalls in the seccomp filter:
e26ac75
89ae9fe
26b1248
a10f52a
9766ee0
4c34815
1330662
462fca2

Comment 8 errata-xmlrpc 2021-11-01 13:35:45 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4042 https://access.redhat.com/errata/RHSA-2021:4042

Comment 9 Product Security DevOps Team 2021-11-01 14:07:50 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-41133

Comment 10 errata-xmlrpc 2021-11-01 16:32:51 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2021:4044 https://access.redhat.com/errata/RHSA-2021:4044

Comment 11 errata-xmlrpc 2021-11-02 18:22:52 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.1 Extended Update Support

Via RHSA-2021:4106 https://access.redhat.com/errata/RHSA-2021:4106

Comment 12 errata-xmlrpc 2021-11-02 20:10:04 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.2 Extended Update Support

Via RHSA-2021:4107 https://access.redhat.com/errata/RHSA-2021:4107


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