This could allow a malicious actor to cause a website to execute website requests to an arbitrary domain of the attacker. This could allow a malicious actor to find sensitive information of other services running on the system.
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.
Patchstack has issued a mitigation rule to block any attacks until an official fix becomes available, can be tested and be safely applied.