Provide references for CVE-2018-20551.
Where can I find more information about CVE-2018-20551?
References are available at: https://gitlab.freedesktop.org/poppler/poppler/merge_requests/146, https://usn.ubuntu.com/3886-1/, https://gitlab.freedesktop.org/poppler/poppler/issues/703, https://access.redhat.com/errata/RHSA-2019:2713.