Microsoft issued a warning over the weekend about an active Linux worm that is targeting a recently disclosed Linux Exim mail server vulnerability. Microsoft states that Azure servers can still be infected or hacked through this vulnerability. Exim is a popular mail server software, or message transfer agent, that is used to send and receive email for its users. Microsoft strongly recommends all Azure users upgrade installed Exim servers to version 4.92, which contains a patch that fixes this flaw. Microsoft suggests that Azure customers utilize Network Security Groups to filter or block traffic to their servers.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-warns-about-worm-attacking-exim-servers-on-azure/