int _gnutls_negotiate_version( gnutls_session_t session, gnutls_protocol_t adv_version)
{
int ret;

  /* if we do not support that version  */
  if (_gnutls_version_is_supported (session, adv_version) == 0)
    {
      /* If he requested something we do not support
       * then we send him the highest we support.
       */
      ret = _gnutls_version_max (session);
      if (ret == GNUTLS_VERSION_UNKNOWN)
	{
	  /* this check is not really needed.
	   */
	  gnutls_assert ();
	  return GNUTLS_E_UNKNOWN_CIPHER_SUITE;
	}
    }
  else
    {
      ret = adv_version;
    }

  _gnutls_set_current_version (session, ret);
    
  return ret;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.