A loss of vacuum accident in the hyperloop tunnel will likely occur during its operation, and it may have a severe impact on its operational safety. Nevertheless, the hyperloop tube breach has only been researched superficially. Two aerodynamic phenomena due to the breach are identified: a (quasi-)steady underexpanded jet and an unsteady blast wave. The overpressure due to the confined blast wave impacting the hyperloop vehicles is determined using various methods. Numerical simulations of the breach applying the 3-dimensional Euler equations show that quasi-1-dimensional (Q1D) approaches only suffice for smaller holes. Although their analytical implementation is less involved than numerical analyses, the Q1D models underpredict the blast wave overpressure, because they cannot account for energy input after the critical shock formation. The (pressure) drag on a vehicle inside the evacuated tube may increase more than an order of magnitude due to the blast wave emanated from the breach location.