gdm3 versions before 3.36.2 or 3.38.2 would start gnome-initial-setup if gdm3 can’t contact the accountservice service via dbus in a timely manner; on Ubuntu (and potentially derivatives) this could be be chained with an additional issue that could allow a local user to create a new privileged account.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-16125
Reference (s):
- https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1900314
- URL: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1900314
- https://gitlab.gnome.org/GNOME/gdm/-/issues/642
- URL: https://gitlab.gnome.org/GNOME/gdm/-/issues/642
- https://securitylab.github.com/advisories/GHSL-2020-202-gdm3-LPE-unresponsive-accounts-daemon