Execute a countermeasure process for vulnerability reliably before an attack aiming at vulnerability occurs. A vulnerability countermeasure processing unit performs a countermeasure process for vulnerability of a vulnerable library function being a general-purpose library function that has vulnerability among the general-purpose library functions included in a general-purpose library. A countermeasure selection unit, when a call for the vulnerable library function is requested at execution of a Web application, makes the vulnerability countermeasure processing unit perform the countermeasure process for the vulnerability of the vulnerable library function, and after the countermeasure process is performed by the vulnerability countermeasure processing unit, calls the vulnerable library function.