Nowadays, the computing and communication services are accessed while on the move. Setting up of fixed access points and backbone infrastructure is not always viable. So in order to provide communication where there is lack of infrastructure or inconvenience in using the existing infrastructure, Mobile Adhoc Networks (MANETs) are used. This inherent flexibility allows MANETs to be used for a wide range of applications such as rescue operations, military applications, vehicular communication, and business meetings. As there is no apriori trust relationship between the nodes of an ad hoc network and basic network functions like packet forwarding and routing are performed by the available nodes, security is an essential component in MANETs. Various attacks in MANETs are blackhole attack, byzantine attack, resource consumption attack, rushing attack, and wormhole attack. Wormhole attack is a severe threat among the other threats in MANET. Existing solutions to detect wormhole attacks include Packet Leashes, SECTOR, DelPHI, RTT-TC, TTM, etc. These solutions require special hardware or strict synchronized clocks or cause message overhead. Some solutions do not locate the wormhole, and some other may generate false alarms or does not consider network congestion into account. In this paper, wormhole attack detection is proposed based on RTT between successive nodes and congestion detection mechanism. If the RTT between two successive nodes is higher than the threshold value, a wormhole attack is suspected. If a wormhole is suspected, node's transitory buffer is probed to determine whether the long delay between the nodes is due to wormhole or not, as delays can be caused due to congestion or by queuing delays. The proposed method prevents both the hidden and the exposed attack. Advantage of our proposed solution is that it does not require any specialized hardware or synchronized clocks.