aiosmptd is a reimplementation of the Python stdlib smtpd.py based on asyncio. Prior to version 1.4.6, servers based on aiosmtpd accept extra unencrypted commands after STARTTLS, treating them as if they came from inside the encrypted connection. This could be exploited by a man-in-the-middle attack. Version 1.4.6 contains a patch for the issue.
Exploitability
AV:AAC:LPR:NUI:NScope
S:UImpact
C:LI:LA:N5.4/CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NOther