Techniques regarding a zero-confidence adversarial attack are provided. For example, one or more embodiments described herein can comprise a system, which can comprise a memory that can store computer executable components. The system can also comprise a processor, operably coupled to the memory, and that can execute the computer executable components stored in the memory. The computer executable components can comprise an adversarial component that computes a perturbation that causes misclassification by a neural network classifier. The computer executable components can also comprise a restoration component that determines a normal vector to a constraint contour developed by the neural network classifier. Further, the computer executable components can comprise a projection component that determines a tangential vector to the constraint contour.