[SECURITY] Prevent reading of any local files in reportlab (CVE-2026-57535)

src/pretix/helpers/apps.py

@@ -30,7 +30,7 @@ class PretixHelpersConfig(AppConfig):
         from .monkeypatching import monkeypatch_all_at_ready
         monkeypatch_all_at_ready()
 
-        # Ensure reportlab does not make any calls to the internet
+        # Ensure reportlab does not make any calls to the internet or the local disk
         from reportlab import rl_config
         rl_config.trustedHosts = []
         rl_config.trustedSchemes = ['data']

src/pretix/helpers/monkeypatching.py

@@ -24,8 +24,11 @@ from datetime import datetime
 from http import cookies
 
 from PIL import Image
+from django.core.exceptions import SuspiciousFileOperation
 from requests.adapters import HTTPAdapter
 
+from pretix.helpers.reportlab import ThumbnailingImageReader
+
 
 def monkeypatch_vobject_performance():
     """
@@ -95,8 +98,26 @@ def monkeypatch_cookie_morsel():
     cookies.Morsel._reserved.setdefault("partitioned", "Partitioned")
 
 
+def monkeypatch_reportlab_imagereader():
+    from reportlab.lib import utils
+    old_init = utils.ImageReader.__init__
+
+    def new_init(self, fileName, ident=None):  # noqa
+        if not isinstance(fileName, Image.Image) and not hasattr(fileName, 'read') and not hasattr(fileName, 'str'):
+            if not isinstance(self, ThumbnailingImageReader):
+                # ThumbnailingImageReader is only used by us explicitly and not by using <img> in html, so it is safe
+                raise SuspiciousFileOperation("reportlab should not be reading images from disk")
+
+        return types.MethodType(old_init, self)(
+            fileName, ident
+        )
+
+    utils.ImageReader.__init__ = new_init
+
+
 def monkeypatch_all_at_ready():
     monkeypatch_vobject_performance()
     monkeypatch_pillow_safer()
     monkeypatch_requests_timeout()
     monkeypatch_cookie_morsel()
+    monkeypatch_reportlab_imagereader()

src/tests/helpers/test_reportlab.py

@@ -20,6 +20,7 @@
 # <https://www.gnu.org/licenses/>.
 #
 import pytest
+from django.core.exceptions import SuspiciousFileOperation
 from reportlab.platypus import Paragraph
 
 
@@ -29,24 +30,21 @@ def test_http_access_disabled(monkeypatch):
 
     monkeypatch.setattr('socket.socket', guard)
 
-    with pytest.raises(OSError, match="Cannot open resource"):
+    with pytest.raises(SuspiciousFileOperation, match="should not be reading images from disk"):
         Paragraph(
             '<img src="https://static.pretix.cloud/static/pretixeu/img/opengraph.png"/>',
         )
 
 
 def test_file_access_disabled_scheme(monkeypatch):
-    with pytest.raises(OSError, match="Cannot open resource"):
+    with pytest.raises(SuspiciousFileOperation, match="should not be reading images from disk"):
         Paragraph(
             '<img src="file:///etc/passwd" />',
         )
 
 
-@pytest.mark.xfail
 def test_file_access_disabled_direct(monkeypatch):
-    # Unfortunately this is not prevented by the reprotlab config, but the risk is low since only valid images
-    # can be used.
-    with pytest.raises(OSError, match="Cannot open resource"):
+    with pytest.raises(SuspiciousFileOperation, match="should not be reading images from disk"):
         Paragraph(
             '<img src="/etc/passwd" />',
         )