The RESTful Web Services (RESTWS) module 7.x-1.x before 7.x-1.3 and 7.x-2.x before 7.x-2.0-alpha5 for Drupal, when page caching is enabled and anonymous users are assigned RESTWS permissions, allows remote attackers to cause a denial of service via a GET request with an HTTP Accept header set to a non-HTML type, which can "interfere with Drupal's page cache."