diff --git a/sapl/base/media.py b/sapl/base/media.py
index 0b7435116..17f8ea518 100644
--- a/sapl/base/media.py
+++ b/sapl/base/media.py
@@ -73,6 +73,14 @@ def _nome_protegido(request, path):
     return arquivo.name[2:] if arquivo.name.startswith('./') else arquivo.name
 
 
+def _caminho_em_media(nome):
+    raiz = os.path.realpath(settings.MEDIA_ROOT)
+    caminho = os.path.realpath(os.path.join(raiz, nome))
+    if not caminho.startswith(raiz + os.sep):
+        raise Http404
+    return caminho
+
+
 def media(request, path):
     partes = path.split('/')
     if any(p in ('', '.', '..') for p in partes) or '\x00' in path:
@@ -93,16 +101,12 @@ def media(request, path):
             tipo_ativo(content_type):
         content_type, disposicao = 'application/octet-stream', 'attachment'
 
+    caminho = _caminho_em_media(nome)
     if settings.DEBUG:
         try:
-            media_root = os.path.realpath(settings.MEDIA_ROOT)
-            caminho = os.path.realpath(os.path.join(media_root, nome))
-            if os.path.commonpath([media_root, caminho]) != media_root:
-                raise Http404
-            response = FileResponse(
-                open(caminho, 'rb'),
-                content_type=content_type)
-        except (FileNotFoundError, IsADirectoryError, ValueError):
+            response = FileResponse(open(caminho, 'rb'),
+                                    content_type=content_type)
+        except (FileNotFoundError, IsADirectoryError):
             raise Http404
     else:
         response = HttpResponse(content_type=content_type)
diff --git a/sapl/base/tests/test_media.py b/sapl/base/tests/test_media.py
index 63366442c..24ceb7156 100644
--- a/sapl/base/tests/test_media.py
+++ b/sapl/base/tests/test_media.py
@@ -276,6 +276,34 @@ def test_debug_serve_arquivo(rf, settings, tmp_path):
             chama(path)
 
 
+@pytest.mark.django_db(transaction=False)
+@pytest.mark.parametrize('debug', [False, True])
+def test_link_simbolico_para_fora_de_media(rf, settings, tmp_path, debug):
+    settings.DEBUG = debug
+    media_root = tmp_path / 'media'
+    fora = tmp_path / 'fora'
+    (media_root / 'sapl/public').mkdir(parents=True)
+    fora.mkdir()
+    (fora / 'segredo.txt').write_bytes(b'segredo')
+    (media_root / 'sapl/public/link').symlink_to(fora)
+    settings.MEDIA_ROOT = str(media_root)
+    request = rf.get('/media/sapl/public/link/segredo.txt')
+    request.user = AnonymousUser()
+
+    with pytest.raises(Http404):
+        media(request, 'sapl/public/link/segredo.txt')
+
+
+@pytest.mark.django_db(transaction=False)
+@pytest.mark.parametrize('path', ['/etc/passwd', 'sapl/public//etc/passwd'])
+def test_caminho_absoluto(rf, path):
+    request = rf.get('/media/' + path)
+    request.user = AnonymousUser()
+
+    with pytest.raises(Http404):
+        media(request, path)
+
+
 @pytest.mark.django_db(transaction=False)
 def test_modelo_protegido_fora_de_private_e_public(client):
     _config('O')
diff --git a/sapl/materia/views.py b/sapl/materia/views.py
index 99f0b4a3c..16376279d 100644
--- a/sapl/materia/views.py
+++ b/sapl/materia/views.py
@@ -16,7 +16,8 @@ from django.conf import settings
 from django.contrib import messages
 from django.contrib.auth.decorators import permission_required
 from django.contrib.auth.mixins import PermissionRequiredMixin
-from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, ValidationError
+from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, \
+    SuspiciousFileOperation, ValidationError
 from django.db import transaction
 from django.db.models import Max, Q
 from django.http import HttpResponse, JsonResponse
@@ -2348,6 +2349,12 @@ class DocumentoAcessorioEmLoteView(PermissionRequiredMixin, FilterView):
                 username, str(msg), request.POST['data']))
             return self.get(request, self.kwargs)
 
+        nome_arquivo = os.path.basename(arquivo.name)
+        if nome_arquivo in ('', '.', '..'):
+            messages.add_message(request, messages.ERROR,
+                                 _('Nome de arquivo inválido.'))
+            return self.get(request, self.kwargs)
+
         # Fora de MEDIA_ROOT, para não ficar acessível em /media/
         with tempfile.NamedTemporaryFile(dir=get_tempfile_dir(),
                                          delete=False) as tmp:
@@ -2380,14 +2387,11 @@ class DocumentoAcessorioEmLoteView(PermissionRequiredMixin, FilterView):
                                          str(doc.id))
                 if not os.path.exists(diretorio):
                     os.makedirs(diretorio)
-                safe_filename = os.path.basename(arquivo.name)
-                file_path = os.path.join(diretorio, safe_filename)
-                real_diretorio = os.path.realpath(diretorio)
-                real_file_path = os.path.realpath(file_path)
-                if os.path.commonpath([real_diretorio, real_file_path]) != real_diretorio:
-                    msg = _('Nome de arquivo inválido.')
-                    messages.add_message(request, messages.ERROR, msg)
-                    return self.get(request, self.kwargs)
+                diretorio = os.path.normpath(diretorio)
+                file_path = os.path.normpath(
+                    os.path.join(diretorio, nome_arquivo))
+                if not file_path.startswith(diretorio + os.sep):
+                    raise SuspiciousFileOperation(nome_arquivo)
                 shutil.copy2(tmp.name, file_path)
                 doc.arquivo.name = file_path.split(
                     MEDIA_ROOT + "/")[1]  # Retira MEDIA_ROOT do nome