We identify vulnerabilities in epidemic forwarding. We address broadcast applications over wireless ad-hoc networks. Epidemic forwarding employs several mechanisms such as inhibition and spread control and each of them can be achieved using different alternative methods. Thus, vulnerabilities existence is highly dependent on the used methods. We examine the links between them. We classify vulnerabilities into two categories: Malicious and rational. We examine the attack impact according to the number of attackers and the different network settings such as density, mobility and congestion. We show that malicious attacks are hard to achieve and their impacts are scenario dependent. In contrast, rational attackers always achieve significant gain. The evaluation is carried out using detailed realistic simulations over networks up to 1000 nodes. We consider static scenarios as well as vehicular networks.