Exim 4 before 4.94.2 allows Out-of-bounds Read. smtp_setup_msg may disclose sensitive information from process memory to an unauthenticated SMTP client.
https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective
https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28023-SCHAD.txt