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 implemented using alternative methods. Thus, the existence of vulnerabilities is highly dependent on the methods used. We examine the links between them. We classify vulnerabilities into two categories: malicious and rational. We examine the effect of the attacks 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 obtain a significant benefit. The evaluation is carried out using detailed realistic simulations over networks with up to 1000 nodes. We consider static scenarios, as well as vehicular networks.