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From 790eb058b0716c536a2f2e8d1c6d5079d776c22b Mon Sep 17 00:00:00 2001
From: Marc Deslauriers <marc.deslauriers@ubuntu.com>
Date: Wed, 30 Apr 2025 10:34:27 -0400
Subject: [PATCH] Fixed CVE-2024-53907 -- Mitigated potential DoS in
strip_tags().
Thanks to jiangniao for the report, and Shai Berger and Natalia Bidart
for the reviews.
CVE: CVE-2024-53907
Upstream-Status: Backport
https://github.com/django/django/commit/790eb058b0716c536a2f2e8d1c6d5079d776c22b
Signed-off-by: Saravanan <saravanan.kadambathursubramaniyam@windriver.com>
---
django/utils/html.py | 10 ++++++++--
docs/releases/3.2.25.txt | 16 ++++++++++++++++
tests/utils_tests/test_html.py | 7 +++++++
3 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/django/utils/html.py b/django/utils/html.py
index 44c6b7b..5887bf1 100644
--- a/django/utils/html.py
+++ b/django/utils/html.py
@@ -8,6 +8,7 @@ from urllib.parse import (
parse_qsl, quote, unquote, urlencode, urlsplit, urlunsplit,
)
+from django.core.exceptions import SuspiciousOperation
from django.utils.encoding import punycode
from django.utils.functional import Promise, keep_lazy, keep_lazy_text
from django.utils.http import RFC3986_GENDELIMS, RFC3986_SUBDELIMS
@@ -30,6 +31,7 @@ simple_url_2_re = _lazy_re_compile(
)
MAX_URL_LENGTH = 2048
+MAX_STRIP_TAGS_DEPTH = 50
@keep_lazy(str, SafeString)
@@ -181,15 +183,19 @@ def _strip_once(value):
@keep_lazy_text
def strip_tags(value):
"""Return the given HTML with all tags stripped."""
- # Note: in typical case this loop executes _strip_once once. Loop condition
- # is redundant, but helps to reduce number of executions of _strip_once.
value = str(value)
+ # Note: in typical case this loop executes _strip_once twice (the second
+ # execution does not remove any more tags).
+ strip_tags_depth = 0
while '<' in value and '>' in value:
+ if strip_tags_depth >= MAX_STRIP_TAGS_DEPTH:
+ raise SuspiciousOperation
new_value = _strip_once(value)
if value.count('<') == new_value.count('<'):
# _strip_once wasn't able to detect more tags.
break
value = new_value
+ strip_tags_depth += 1
return value
diff --git a/docs/releases/3.2.25.txt b/docs/releases/3.2.25.txt
index 67dc8a2..f21bb47 100644
--- a/docs/releases/3.2.25.txt
+++ b/docs/releases/3.2.25.txt
@@ -66,6 +66,22 @@ CVE-2024-41991: Potential denial-of-service vulnerability in ``django.utils.html
subject to a potential denial-of-service attack via certain inputs with a very
large number of Unicode characters.
+CVE-2024-53907: Denial-of-service possibility in ``strip_tags()``
+=================================================================
+
+:func:`~django.utils.html.strip_tags` would be extremely slow to evaluate
+certain inputs containing large sequences of nested incomplete HTML entities.
+The ``strip_tags()`` method is used to implement the corresponding
+:tfilter:`striptags` template filter, which was thus also vulnerable.
+
+``strip_tags()`` now has an upper limit of recursive calls to ``HTMLParser``
+before raising a :exc:`.SuspiciousOperation` exception.
+
+Remember that absolutely NO guarantee is provided about the results of
+``strip_tags()`` being HTML safe. So NEVER mark safe the result of a
+``strip_tags()`` call without escaping it first, for example with
+:func:`django.utils.html.escape`.
+
Bugfixes
========
diff --git a/tests/utils_tests/test_html.py b/tests/utils_tests/test_html.py
index 93458ac..231f5d8 100644
--- a/tests/utils_tests/test_html.py
+++ b/tests/utils_tests/test_html.py
@@ -1,6 +1,7 @@
import os
from datetime import datetime
+from django.core.exceptions import SuspiciousOperation
from django.test import SimpleTestCase
from django.utils.functional import lazystr
from django.utils.html import (
@@ -92,12 +93,18 @@ class TestUtilsHtml(SimpleTestCase):
('<script>alert()</script>&h', 'alert()h'),
('><!' + ('&' * 16000) + 'D', '><!' + ('&' * 16000) + 'D'),
('X<<<<br>br>br>br>X', 'XX'),
+ ("<" * 50 + "a>" * 50, ""),
)
for value, output in items:
with self.subTest(value=value, output=output):
self.check_output(strip_tags, value, output)
self.check_output(strip_tags, lazystr(value), output)
+ def test_strip_tags_suspicious_operation(self):
+ value = "<" * 51 + "a>" * 51, "<a>"
+ with self.assertRaises(SuspiciousOperation):
+ strip_tags(value)
+
def test_strip_tags_files(self):
# Test with more lengthy content (also catching performance regressions)
for filename in ('strip_tags1.html', 'strip_tags2.txt'):
--
2.40.0
|
