diff --git a/inyoka/middlewares/common.py b/inyoka/middlewares/common.py
index a10d9823c..4e183b209 100644
--- a/inyoka/middlewares/common.py
+++ b/inyoka/middlewares/common.py
@@ -16,6 +16,7 @@
 """
 from django.conf import settings
 from django.contrib import messages
+from django.http import HttpResponse
 from django.middleware.common import CommonMiddleware
 from django_hosts.middleware import HostsRequestMiddleware
 
@@ -35,7 +36,13 @@ def process_request(self, request):
         request.watch = StopWatch()
         request.watch.start()
 
-        # IMPORTANT: Since we run some setupcode (mainly locals), this middleware
+        # reject URLs with NUL byte.
+        # If those are passed to the ORM with postgres, an exception is raised
+        # It's also mentioned in https://datatracker.ietf.org/doc/html/rfc3986#section-7.3
+        if '\x00' in request.path:
+            return HttpResponse(content='The URL contained NUL characters', status=400, content_type='text/plain')
+
+        # IMPORTANT: Since we run some setup-code (mainly locals), this middleware
         # needs to be the first one, hence we manually dispatch to HostsMiddleware
         response = HostsRequestMiddleware.process_request(self, request)
         if response is not None:
diff --git a/tests/utils/test_middleware.py b/tests/utils/test_middleware.py
new file mode 100644
index 000000000..7b24c515d
--- /dev/null
+++ b/tests/utils/test_middleware.py
@@ -0,0 +1,27 @@
+"""
+    tests.apps.utils.test_middleware
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Test Inyoka-custom middlewares.
+
+    :copyright: (c) 2012-2023 by the Inyoka Team, see AUTHORS for more details.
+    :license: BSD, see LICENSE for more details.
+"""
+from django.conf import settings
+
+from inyoka.utils.test import InyokaClient, TestCase
+
+
+class TestNULByte(TestCase):
+
+    client_class = InyokaClient
+
+    def test_get_null(self):
+        url = f'http://{ settings.BASE_DOMAIN_NAME }/1%00%EF/'
+        response = self.client.get(url)
+        self.assertEqual(response.status_code, 400)
+
+    def test_get_null_calender(self):
+        url = f'http://{ settings.BASE_DOMAIN_NAME }/2023/11/18/lpd-2023-10\x00EF2522/ics/'
+        response = self.client.get(url)
+        self.assertEqual(response.status_code, 400)