Validation Attribute do some kind of caching?
public class CurrentPasswordValidationAttribute : ValidationAttribute
{
    private IWorkContext workContext;
    private ICryptoService cryptoService;

    public CurrentPasswordValidationAttribute() : this(IoCContainer.Resolve<IWorkContext>(), IoCContainer.Resolve<ICryptoService>()) { }

    public CurrentPasswordValidationAttribute(IWorkContext workContext, ICryptoService cryptoService)
    {
        this.workContext = workContext;
        this.cryptoService = cryptoService;
    }

    public override bool IsValid(object value)
    {
        if (value == null)
            return true;

        var user = workContext.CurrentUser;
        //var user = IoCContainer.Resolve<IWorkContext>().CurrentUser;

        return user.Password.SaltedAndHashedPassword == cryptoService.HashStringWithSHA256(string.Concat(value.ToString(), user.Password.Salt));
    }
}

public User CurrentUser
    {
        get
        {
            return userService.GetUserByEmail(HttpContext.Current.User.Identity.Name);
        }
    }