Vulnerability in the MySQL Connectors component of Oracle MySQL (subcomponent: Connector/C). Supported versions that are affected are 6.1.10 and earlier. Difficult to exploit vulnerability allows low privileged attacker with network access via multiple protocols to compromise MySQL Connectors. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Connectors. Note: The documentation has also been updated for the correct way to use mysqlstmtclose(). Please see: https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-execute.html, https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-fetch.html, https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-close.html, https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-error.html, https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-errno.html, and https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-sqlstate.html. CVSS 3.0 Base Score 5.3 (Availability impacts). CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H).

Oracle MySQL before 5.7.3, Oracle MySQL Connector/C (aka libmysqlclient) before 6.1.3, and MariaDB before 5.5.44 use the --ssl option to mean that SSL is optional, which allows man-in-the-middle attackers to spoof servers via a cleartext-downgrade attack, aka a "BACKRONYM" attack.