Pass taxonomy terms from node to block
/**
 * Override or insert variables into the block templates.
 *
 * @param $variables
 *   An array of variables to pass to the theme template.
 * @param $hook
 *   The name of the template being rendered ("block" in this case.)
 */

function MYTHEME_preprocess_block(&amp;$variables) {

  if ($variables['block_id'] == 'target_block_id') {

    //load node object
    $node = menu_get_object();

    // do something with node object

    // add variable to your block template file
    $variables['block_variable'] = 'something';
  }
}


Available block variables - Block variables