Fetchmail before 6.4.22 fails to enforce STARTTLS session encryption in some circumstances, such as a certain situation with IMAP and PREAUTH.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:HI:NA:N5.9/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N