Rule Definition
When a Servlet throws an exception, the default error response the Servlet container sends back to the user typically includes debugging information. This information is of great value to an attacker. For example, a stack trace might show the attacker a malformed SQL query string, the type of database being used, and the version of the application container. This information enables the attacker to target known vulnerabilities in these components.

Remediation
Use of try-catch block is recommended.

Violation Code Sample

@WebServlet(name = "Hello", value = ["/hello"])
class Test123 : HttpServlet() {
    @Throws(IOException::class) //Violation
    override fun doGet(req: HttpServletRequest, res: HttpServletResponse) {
        val ip: String = req.getRemoteAddr()
        val addr: InetAddress = InetAddress.getByName(ip)
        .
        .
        .
        out.println("hello " + addr.getHostName())
    } 
}

Fixed Code Sample

@WebServlet(name = "Hello", value = ["/hello"])
class Test123 : HttpServlet() {
    override fun doGet(req: HttpServletRequest, res: HttpServletResponse) {
        try{   //Violation fixed
          val ip: String = req.getRemoteAddr()
          val addr: InetAddress = InetAddress.getByName(ip)
          .
          .
          .
          out.println("hello " + addr.getHostName())
        }
        catch(unknownhostexception uhex){
             out.println("123")
             .
             .
        } 
    }
}

http://cwe.mitre.org/data/definitions/600.html