Jenkins 2.587 and earlier, LTS 2.580.1 and earlier does not consistently enforce the restriction on deserializing objects of types marked as storing t

Summary

Jenkins 2.587 and earlier, LTS 2.580.1 and earlier does not consistently enforce the restriction on deserializing objects of types marked as storing their configuration in independent top-level configuration files as nested values, allowing attackers to bypass the root element check and potentially inject nested objects.

Remediation

1. Inventory every Jenkins Jenkins deployment, including staging.
2. Upgrade Jenkins Jenkins to the fixed version for your release line, listed under Affected versions.
3. Confirm the running version after the upgrade.

References

• Advisoryhttps://www.jenkins.io/security/advisory/2026-10-28/#SECURITY-4243