An issue was discovered in GitLab Community and Enterprise Edition 8.14 through 12.2.1. The Jira integration contains a SSRF vulnerability as a result of a bypass of the current protection mechanisms against this type of attack, which would allow sending requests to any resources accessible in the local network by the GitLab server.
https://gitlab.com/gitlab-org/gitlab-ce/issues/61349
https://about.gitlab.com/2019/08/29/security-release-gitlab-12-dot-2-dot-3-released/