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.

The (1) git-remote-ext and (2) unspecified other remote helper programs in Git before 2.3.10, 2.4.x before 2.4.10, 2.5.x before 2.5.4, and 2.6.x before 2.6.1 do not properly restrict the allowed protocols, which might allow remote attackers to execute arbitrary code via a URL in a (a) .gitmodules file or (b) unknown other sources in a submodule.