--- a/management/univention-management-console-module-udm/src/univention/management/modules/udm/module.py	
+++ a/management/univention-management-console-module-udm/src/univention/management/modules/udm/module.py	
@@ -457,7 +457,7 @@ class RessourceBase(object):
 	def decode_request_arguments(self):
 		content_type = self.request.headers.get('Content-Type', '')
 		if self.request.method in ('HEAD', 'GET', 'OPTIONS') and content_type:
-			raise HTTPError(400, 'safe HTTP method should not contain request body/content-type')
+			return
 		if content_type.startswith('application/json'):
 			try:
 				self.request.body_arguments = json.loads(self.request.body)