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.
Created sddm tracking bugs for this issue:
Affects: epel-all [bug 1894659]
Affects: fedora-all [bug 1894658]
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.