Jenkins Deserialization of Untrusted Data Vulnerability - CVE-2026-53435

In Jenkins 2.567 and earlier LTS 2.555.2 and earlier it is possible for attackers to have Jenkins deserialize arbitrary types defined in Jenkins core or plugins from an attacker-controlled config.xml submission in a way that allows them to handle HTTP requests afterwards. This can be used to impersonate any user and send HTTP requests on their behalf up to and including use of the Script Console to run arbitrary code or to read arbitrary files from the Jenkins controller.