In this paper we consider the problem ofdis-turbance attenuation with internal stabilityfor nonlinear,input-affine systems via measurement feedback. The solu-tion to the above problem has been provided, three decadesago, in terms of the solution to a system of coupled non-linear, first-order partial differential equations (PDEs). Asa consequence, despite the rather elegant characterizationof the solution, the presence of PDEs renders the controldesign synthesis almost infeasible in practice. Therefore, tocircumvent such a computational bottle-neck, in this paperwe provide a novel characterization of the exact solution tothe problem that does not hinge upon theexplicitcompu-tation of the solution to any PDE. The result is achieved byconsidering theimmersionof the nonlinear dynamics intoan extended system for which locally positive definite func-tions solving the required PDEs may be directly provided inclosed-formby relying only on the solutions to Riccati-like,state-dependent, algebraic matrix equations.