In Jenkins 2.579 and earlier, LTS 2.568.2 and earlier, the REST API and CLI endpoints for updating agent configuration do not prevent a submitted configuration from overwriting a different agent by specifying that agent's name in the submitted XML document, allowing attackers with Agent/Configure permission on one agent to take over a different agent, gaining control of its configuration and obtaining access to its inbound agent secret and environment variables.
https://www.jenkins.io/security/advisory/2026-09-02/#SECURITY-4025