The DBD::mysql module through 4.043 for Perl uses the mysql_ssl=1 setting to mean that SSL is optional (even though this setting's documentation has a "your communication with the server will be encrypted" statement), which allows man-in-the-middle attackers to spoof servers via a cleartext-downgrade attack, a related issue to CVE-2015-3152.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:NI:HA:N5.9/CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N