Safe implementation for extending authentication cookie with user data

After searching around and reading through articles and answers I came up with this implementation for extending the cookie of Forms Authentication. But I am not 100% sure that I did not introduce any vulnerabilities and now I provided here for review.

    public ActionResult LogOn(LogOnModel model, string returnUrl)
    {
//... other code
        // old implementation     
        FormsAuthentication.SetAuthCookie(model.Username, model.RememberMe); 
        string userData = "userdata";
        var cookie = ExtendAuthCookie(FormsAuthentication.GetAuthCookie(model.Username, model.RememberMe), userData);
        System.Web.HttpContext.Current.Response.Cookies.Add(cookie);
//... other code
    }

    private HttpCookie ExtendAuthCookie(HttpCookie authCookie, string userData)
    {
        var originalTicket = GetOriginalTicket(authCookie);
        System.Web.Security.FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(
           2, 
           originalTicket.Name, 
           originalTicket.IssueDate, 
           originalTicket.Expiration, 
           originalTicket.IsPersistent, 
           userData, // Extending with user data
           originalTicket.CookiePath 
           );


        String strTicket = FormsAuthentication.Encrypt(ticket);
        if (string.IsNullOrEmpty(strTicket))
        {
            throw new HttpException("Unable to encrypt cookie ticket.");
        }

        HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, strTicket);

        cookie.HttpOnly = true;
        cookie.Secure = true;

        return cookie;
    }

    private FormsAuthenticationTicket GetOriginalTicket(HttpCookie authCookie)
    {
        var cookie = System.Web.HttpContext.Current.Request.Cookies[FormsAuthentication.FormsCookieName];
        if (cookie == null)
        {
            throw new ArgumentNullException("cookie");
        }

        var ticket = FormsAuthentication.Decrypt(cookie.Value);
        if (ticket == null)
        {
            throw new ArgumentNullException("ticket");
        }

        if (ticket.Expired)
        {
            throw new InvalidOperationException("ticket");
        }

        return ticket;
    }