Legal analysis: it needs to be handled again. If the master contract is changed, the mortgage contract as a subordinate contract must also be changed, because the previous mortgage period is different.

(1) The principal creditor's rights are extinguished.

(2) the realization of security interests;

(3) The creditor waives the security interest.

(4) Other circumstances in which the security interest is extinguished as stipulated by law.

The mortgage period expires. Generally speaking, although the mortgage right cannot be extinguished due to the extinguishment of the principal creditor's rights, it should not exist forever for the sake of stabilizing civil relations and maintaining social order, but should exist for a certain period, which is a predetermined period in nature.

Legal basis: Article 692 of the Civil Code of People's Republic of China (PRC) * * * The guarantee period is the period that the guarantor decides to undertake the guarantee responsibility, and it is not suspended, interrupted or extended. The creditor and the guarantor may agree on a guarantee period, but if the agreed guarantee period expires before or at the same time as the performance period of the principal debt, it is deemed that there is no agreement; If there is no agreement or the agreement is unclear, the guarantee period shall be six months from the date of expiration of the main debt performance period. Where the creditor and the debtor have not agreed or clearly agreed on the time limit for the performance of the principal debt, the guarantee period shall be counted from the date when the grace period for the creditor to request the debtor to perform the debt expires.