To reproduce this issue as following steps.
1. Create two articles in knowledge base (Admin) in control panel, one is as draft, the other is as published.
2. Add Knowledge Base (Display) portlet in page.
3. Click "Administrator", you can see two articles.
a. Can see details of the published article in clicking the link of it.
b. Can NOT see details of the draft article in clicking the link of it.
In b case, even Administrator role use cannot see the draft and error is printed into catalina.out (see error.log).