The nonlinear feedforward generator is one of the commonly used building blocks of stream ciphers. This paper describes a novel known-plaintext attack for cryptanalyzing nonlinear feedforward generator. The plaintext requirement of the attack is only twice the length of the shift register. The implementation of this attack could identify the initial settings of the system for a 128 stage register and randomly chosen nonlinear feedforward function of 10 variables in few minutes on a P-II 300 MHz machine.