Agent-to-controller security bypass in Jenkins Semantic Versioning Plugin

Jenkins Semantic Versioning Plugin defines a controller/agent message that processes a given file as XML and returns version information. The XML parser is not configured to prevent XML external entity (XXE) attacks, which is only a problem if XML documents are parsed on the Jenkins controller.

Jenkins Semantic Versioning Plugin 1.13 and earlier does not restrict execution of a controller/agent message to agents, and implements no limitations about the file path that can be parsed, allowing attackers able to control agent processes to have Jenkins parse a crafted file that uses external entities for extraction of secrets from the Jenkins controller or server-side request forgery.

This vulnerability is only exploitable in Jenkins 2.318 and earlier, LTS 2.303.2 and earlier. See the LTS upgrade guide.