The /plugins/servlet/gadgets/makeRequest resource in Jira before version 8.4.0 allows remote attackers to access the content of internal network resources via a Server Side Request Forgery (SSRF) vulnerability due to a logic bug in the JiraWhitelist class.
https://github.com/b0ul1/CVE-2019-8451
https://github.com/pwnosec/jira-vuln-scanner
https://github.com/imhunterand/JiraCVE