Git Plugin connects to a user-specified Git repository as part of form validation. An attacker with no direct access to Jenkins but able to guess at a username/password credentials ID could trick a developer with job configuration permissions into following a link with a maliciously crafted Jenkins URL which would result in the Jenkins Git client sending the username and password to an attacker-controlled server.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-1000092
• https://jenkins.io/security/advisory/2017-07-10/
• https://bugzilla.redhat.com/show_bug.cgi?id=1471053