As immediate action, update the affected plugin. If you're unable to do so, ask your hosting provider or web developer for help.
This vulnerability affects all WordPress core versions, and at this point is not something that is likely to be fixed anytime soon. This vulnerability is of low severity and has no meaningful impact on the average site.
Attackers can make the server connect to internal systems and leak data from behind the firewall.
CVSS score is a way to evaluate and rank reported vulnerabilities in a standardized and repeatable way but which is not ideal for WordPress.
This security issue has a low severity impact and is unlikely to be exploited.