Exim 4 before 4.94.2 has Improper Neutralization of Line Delimiters. Local users can alter the behavior of root processes because a recipient address can have a newline character.
https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective
https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28015-NLEND.txt