Fairness and stability guarantee among TCP flows is very stubborn in wireless ad hoc networks. There is not a MAC protocol that can fulfill this acquirement until now. In this paper, we firstly reveal the in-depth causes of the severe TCP unfairness and instability problems in IEEE 802.11-based multihop networks. Then we utilize the collision detection mechanism of the IEEE 802.11 protocol which is often ignored by most of the people to design a novel collision detection mechanism-based MAC (CDMB-MAC) scheme to solve the short-term and long-term fairness and stability issues while providing a good aggregate throughput in many topologies.