Apache VCL versions 2.1 through 2.5 do not properly validate form input when adding and removing VMs to and from hosts. The form data is then used in SQL statements. This allows for an SQL injection attack. Access to this portion of a VCL system requires admin level rights. Other layers of security seem to protect against malicious attack. However, all VCL systems running versions earlier than 2.5.1 should be upgraded or patched. This vulnerability was found and reported to the Apache VCL project by ADLab of Venustech.