Discuss defenses available to the promisor in an action by an intended third-party beneficiary to enforce the promise.

In an action by an intended beneficiary to enforce the promise, the promisor may assert any defense that would be available to him if the action had been brought by the promisee. The rights of the third party are based on the promisor's contract with the promisee. The promisor may assert such defenses as absence of mutual assent or consideration, lack of capacity, fraud, or mistake. After an intended beneficiary's rights have vested, the promisor may not assert the defense of contractual modification or rescission entered into with the promisee.