[4.2.x] Fixed CVE-2025-26699 -- Mitigated potential DoS in wordwrap template filter.

sarahboyce · sarahboyce · commit e88f7376fe68 · 2025-03-06T10:01:44.000+01:00
Thanks sw0rd1ight for the report. Backport of 55d89e2 from main.
diff --git a/django/utils/text.py b/django/utils/text.py
@@ -1,6 +1,7 @@
 import gzip
 import re
 import secrets
+import textwrap
 import unicodedata
 from gzip import GzipFile
 from gzip import compress as gzip_compress
@@ -97,24 +98,15 @@ def wrap(text, width):
     ``width``.
     """
 
-    def _generator():
-        for line in text.splitlines(True):  # True keeps trailing linebreaks
-            max_width = min((line.endswith("\n") and width + 1 or width), width)
-            while len(line) > max_width:
-                space = line[: max_width + 1].rfind(" ") + 1
-                if space == 0:
-                    space = line.find(" ") + 1
-                    if space == 0:
-                        yield line
-                        line = ""
-                        break
-                yield "%s\n" % line[: space - 1]
-                line = line[space:]
-                max_width = min((line.endswith("\n") and width + 1 or width), width)
-            if line:
-                yield line
-
-    return "".join(_generator())
+    wrapper = textwrap.TextWrapper(
+        width=width,
+        break_long_words=False,
+        break_on_hyphens=False,
+    )
+    result = []
+    for line in text.splitlines(True):
+        result.extend(wrapper.wrap(line))
+    return "\n".join(result)
 
 
 class Truncator(SimpleLazyObject):
diff --git a/docs/releases/4.2.20.txt b/docs/releases/4.2.20.txt
@@ -5,3 +5,9 @@ Django 4.2.20 release notes
 *March 6, 2025*
 
 Django 4.2.20 fixes a security issue with severity "moderate" in 4.2.19.
+
+CVE-2025-26699: Potential denial-of-service vulnerability in ``django.utils.text.wrap()``
+=========================================================================================
+
+The ``wrap()`` and :tfilter:`wordwrap` template filter were subject to a
+potential denial-of-service attack when used with very long strings.
diff --git a/tests/template_tests/filter_tests/test_wordwrap.py b/tests/template_tests/filter_tests/test_wordwrap.py
@@ -78,3 +78,14 @@ def test_wrap_lazy_string(self):
             "this is a long\nparagraph of\ntext that\nreally needs\nto be wrapped\n"
             "I'm afraid",
         )
+
+    def test_wrap_long_text(self):
+        long_text = (
+            "this is a long paragraph of text that really needs"
+            " to be wrapped I'm afraid " * 20_000
+        )
+        self.assertIn(
+            "this is a\nlong\nparagraph\nof text\nthat\nreally\nneeds to\nbe wrapped\n"
+            "I'm afraid",
+            wordwrap(long_text, 10),
+        )
