Linux – Exim MTA VULN
The vulnerability, which has been assigned the identifier CVE-2018-6789, is present in all versions of Exim prior to 4.90.1, which was released to patch this issue.
According to a research report published this month by SecuritySpace, 556,000 identifiable mail servers ran Exim.
A search for Exim instances on Shodan shows just short of 4.5 million instances are running.