A brake actuator for a commercial vehicle, the brake actuator comprising: - a housing , - a piston that is movably mounted inside the housing and configured to reciprocate along a stroke axis (S) between a retracted position and an extended position for applying and releasing a braking force to and from a brake mechanism of the vehicle, and - an electric motor that is operatively coupled to the piston and configured to move the piston between the retracted and extended positions such as to apply and release the braking force wherein the electric motor is coupled to a screw drive , and the screw drive is coupled to the piston and configured to transfer a rotational drive movement of the electric motor into the movement of the piston and wherein the screw drive comprises a rotating element and a nut , wherein the rotating element and the nut are in thread engagement and wherein the rotating element is rotatably mounted in the housing , and the nut is a running nut that is movably mounted to the rotating element and rests against the piston and wherein the piston is slidably supported in the housing , configured to move along the stroke axis (S) and wherein a radially expandable sealing element is positioned in the peripheral region of the piston , such that it sealingly abuts against an inside wall of the housing characterized in that the piston is configured to pivot from the stroke axis (S) within a predetermined angle (α) to account for lateral movements imposed by the externally mounted brake mechanism and the nut comprises an end face that faces the piston and comprises a convexly shaped surface portion . - a housing , - a piston that is movably mounted inside the housing and configured to reciprocate along a stroke axis (S) between a retracted position and an extended position for applying and releasing a braking force to and from a brake mechanism of the vehicle, and - an electric motor that is operatively coupled to the piston and configured to move the piston between the retracted and extended positions such as to apply and release the braking force wherein the electric motor is coupled to a screw drive , and the screw drive is coupled to the piston and configured to transfer a rotational drive movement of the electric motor into the movement of the piston and wherein the screw drive comprises a rotating element and a nut , wherein the rotating element and the nut are in thread engagement and wherein the rotating element is rotatably mounted in the housing , and the nut is a running nut that is movably mounted to the rotating element and rests against the piston and wherein the piston is slidably supported in the housing , configured to move along the stroke axis (S) and wherein a radially expandable sealing element is positioned in the peripheral region of the piston , such that it sealingly abuts against an inside wall of the housing characterized in that the piston is configured to pivot from the stroke axis (S) within a predetermined angle (α) to account for lateral movements imposed by the externally mounted brake mechanism and the nut comprises an end face that faces the piston and comprises a convexly shaped surface portion . <EOS>