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Gentoo Linux Security Advisory                           GLSA 202402-02
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                                           https://security.gentoo.org/
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 Severity: Normal
    Title: SDDM: Privilege Escalation
     Date: February 03, 2024
     Bugs: #753104
       ID: 202402-02

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Synopsis
========

A vulnerability has been discovered in SDDM which can lead to privilege
escalation.

Background
==========

SDDM is a modern display manager for X11 and Wayland sessions aiming to
be fast, simple and beautiful. It uses modern technologies like QtQuick,
which in turn gives the designer the ability to create smooth, animated
user interfaces.

Affected packages
=================

Package        Vulnerable    Unaffected
-------------  ------------  ------------
x11-misc/sddm  < 0.18.1-r6   >= 0.18.1-r6

Description
===========

A vulnerability has been discovered in SDDM. Please review the CVE
identifier referenced below for details.

Impact
======

SDDM passes the -auth and -displayfd command line arguments when
starting the Xserver. It then waits for the display number to be
received from the Xserver via the `displayfd`, before the Xauthority
file specified via the `-auth` parameter is actually written. This
results in a race condition, creating a time window in which no valid
Xauthority file is existing while the Xserver is already running.

The X.Org server, when encountering a non-existing, empty or
corrupt/incomplete Xauthority file, will grant any connecting client
access to the Xorg display. A local unprivileged attacker can thus
create an unauthorized connection to the Xserver and grab e.g. keyboard
input events from other legitimate users accessing the Xserver.

Workaround
==========

There is no known workaround at this time.

Resolution
==========

All SDDM users should upgrade to the latest version:

  # emerge --sync
  # emerge --ask --oneshot --verbose ">=x11-misc/sddm-0.18.1-r6"

References
==========

[ 1 ] CVE-2020-28049
      https://nvd.nist.gov/vuln/detail/CVE-2020-28049

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

 https://security.gentoo.org/glsa/202402-02

Concerns?
=========

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users' machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
https://bugs.gentoo.org.

License
=======

Copyright 2024 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

https://creativecommons.org/licenses/by-sa/2.5