Smart card Web server provides a modern interface between smart cards and the external world. It is of paramount importance that this new software component does not jeopardize the security of the smart card. This paper presents a formal model of the smart card Web server specification and the proof of its security properties. The formalization enables a thoughtful analysis of the specification that has revealed several ambiguities and potentially dangerous behaviors. Our formal model is built using a modular approach upon a model of Java Card and Global Platform. By proving the security properties, we show that the smart card Web server preserves the security policy of the overall model. In other words, this component introduces no illegal access to the card resources (i.e., file system and applications). Furthermore, the smart card Web server provides a means for securely managing the card contents (i.e., resources update).