This issue is similar to issue 8. If the Home Agent doesn’t recognize the Challenge extension, it sends a Registration Reply to the Foreign Agent without Challenge extension (section 3.4). When the Foreign Agent receives the Registration Reply from the Home Agent without challenge extension, it includes a new challenge extension (section 3.3) in the Registration Reply prior to forwarding it to the Mobile Node. In this case, the Registration Request is not Rejected as indicated in the issue text.
There are no modifications proposed for this issue in RFC3012bis draft.