From 9e9792228a6bb5d6402a5d645bc3be4cf364aefb Mon Sep 17 00:00:00 2001
From: Sarah Boyce <42296566+sarahboyce@users.noreply.github.com>
Date: Wed, 26 Jun 2024 12:11:54 +0200
Subject: [PATCH] Fixed CVE-2024-39614 -- Mitigated potential DoS in
get_supported_language_variant().
Language codes are now parsed with a maximum length limit of 500 chars.
Thanks to MProgrammer for the report.
---
django/utils/translation/trans_real.py | 25 ++++++++++++++++++++-----
docs/ref/utils.txt | 10 ++++++++++
docs/releases/4.2.14.txt | 15 +++++++++++++++
docs/releases/5.0.7.txt | 15 +++++++++++++++
tests/i18n/tests.py | 11 +++++++++++
5 files changed, 71 insertions(+), 5 deletions(-)
diff --git a/django/utils/translation/trans_real.py b/django/utils/translation/trans_real.py
index a629528717f..4439fdad3f3 100644
--- a/django/utils/translation/trans_real.py
+++ b/django/utils/translation/trans_real.py
@@ -32,9 +32,10 @@ _default = None
CONTEXT_SEPARATOR = "\x04"
# Maximum number of characters that will be parsed from the Accept-Language
-# header to prevent possible denial of service or memory exhaustion attacks.
-# About 10x longer than the longest value shown on MDN’s Accept-Language page.
-ACCEPT_LANGUAGE_HEADER_MAX_LENGTH = 500
+# header or cookie to prevent possible denial of service or memory exhaustion
+# attacks. About 10x longer than the longest value shown on MDN’s
+# Accept-Language page.
+LANGUAGE_CODE_MAX_LENGTH = 500
# Format of Accept-Language header values. From RFC 9110 Sections 12.4.2 and
# 12.5.4, and RFC 5646 Section 2.1.
@@ -498,11 +499,25 @@ def get_supported_language_variant(lang_code, strict=False):
If `strict` is False (the default), look for a country-specific variant
when neither the language code nor its generic variant is found.
+ The language code is truncated to a maximum length to avoid potential
+ denial of service attacks.
+
lru_cache should have a maxsize to prevent from memory exhaustion attacks,
as the provided language codes are taken from the HTTP request. See also
.
"""
if lang_code:
+ # Truncate the language code to a maximum length to avoid potential
+ # denial of service attacks.
+ if len(lang_code) > LANGUAGE_CODE_MAX_LENGTH:
+ if (
+ not strict
+ and (index := lang_code.rfind("-", 0, LANGUAGE_CODE_MAX_LENGTH)) > 0
+ ):
+ # There is a generic variant under the maximum length accepted length.
+ lang_code = lang_code[:index]
+ else:
+ raise ValueError("'lang_code' exceeds the maximum accepted length")
# If 'zh-hant-tw' is not supported, try special fallback or subsequent
# language codes i.e. 'zh-hant' and 'zh'.
possible_lang_codes = [lang_code]
@@ -626,13 +641,13 @@ def parse_accept_lang_header(lang_string):
functools.lru_cache() to avoid repetitive parsing of common header values.
"""
# If the header value doesn't exceed the maximum allowed length, parse it.
- if len(lang_string) <= ACCEPT_LANGUAGE_HEADER_MAX_LENGTH:
+ if len(lang_string) <= LANGUAGE_CODE_MAX_LENGTH:
return _parse_accept_lang_header(lang_string)
# If there is at least one comma in the value, parse up to the last comma
# before the max length, skipping any truncated parts at the end of the
# header value.
- if (index := lang_string.rfind(",", 0, ACCEPT_LANGUAGE_HEADER_MAX_LENGTH)) > 0:
+ if (index := lang_string.rfind(",", 0, LANGUAGE_CODE_MAX_LENGTH)) > 0:
return _parse_accept_lang_header(lang_string[:index])
# Don't attempt to parse if there is only one language-range value which is
diff --git a/docs/ref/utils.txt b/docs/ref/utils.txt
index 9fb1e83e9e2..65dc9952bcc 100644
--- a/docs/ref/utils.txt
+++ b/docs/ref/utils.txt
@@ -1147,6 +1147,11 @@ For a complete discussion on the usage of the following see the
``lang_code`` is ``'es-ar'`` and ``'es'`` is in :setting:`LANGUAGES` but
``'es-ar'`` isn't.
+ ``lang_code`` has a maximum accepted length of 500 characters. A
+ :exc:`ValueError` is raised if ``lang_code`` exceeds this limit and
+ ``strict`` is ``True``, or if there is no generic variant and ``strict``
+ is ``False``.
+
If ``strict`` is ``False`` (the default), a country-specific variant may
be returned when neither the language code nor its generic variant is found.
For example, if only ``'es-co'`` is in :setting:`LANGUAGES`, that's
@@ -1155,6 +1160,11 @@ For a complete discussion on the usage of the following see the
Raises :exc:`LookupError` if nothing is found.
+ .. versionchanged:: 4.2.14
+
+ In older versions, ``lang_code`` values over 500 characters were
+ processed without raising a :exc:`ValueError`.
+
.. function:: to_locale(language)
Turns a language name (en-us) into a locale name (en_US).
diff --git a/docs/releases/4.2.14.txt b/docs/releases/4.2.14.txt
index dc20cd9f28c..08523e27fd2 100644
--- a/docs/releases/4.2.14.txt
+++ b/docs/releases/4.2.14.txt
@@ -32,3 +32,18 @@ directory-traversal via certain inputs when calling :meth:`save()
`.
Built-in ``Storage`` sub-classes were not affected by this vulnerability.
+
+CVE-2024-39614: Potential denial-of-service vulnerability in ``get_supported_language_variant()``
+=================================================================================================
+
+:meth:`~django.utils.translation.get_supported_language_variant` was subject to
+a potential denial-of-service attack when used with very long strings
+containing specific characters.
+
+To mitigate this vulnerability, the language code provided to
+:meth:`~django.utils.translation.get_supported_language_variant` is now parsed
+up to a maximum length of 500 characters.
+
+When the language code is over 500 characters, a :exc:`ValueError` will now be
+raised if ``strict`` is ``True``, or if there is no generic variant and
+``strict`` is ``False``.
diff --git a/docs/releases/5.0.7.txt b/docs/releases/5.0.7.txt
index c09e2d7040d..148a2e25b3d 100644
--- a/docs/releases/5.0.7.txt
+++ b/docs/releases/5.0.7.txt
@@ -33,6 +33,21 @@ directory-traversal via certain inputs when calling :meth:`save()
Built-in ``Storage`` sub-classes were not affected by this vulnerability.
+CVE-2024-39614: Potential denial-of-service vulnerability in ``get_supported_language_variant()``
+=================================================================================================
+
+:meth:`~django.utils.translation.get_supported_language_variant` was subject to
+a potential denial-of-service attack when used with very long strings
+containing specific characters.
+
+To mitigate this vulnerability, the language code provided to
+:meth:`~django.utils.translation.get_supported_language_variant` is now parsed
+up to a maximum length of 500 characters.
+
+When the language code is over 500 characters, a :exc:`ValueError` will now be
+raised if ``strict`` is ``True``, or if there is no generic variant and
+``strict`` is ``False``.
+
Bugfixes
========
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index 355505a10d1..1bd1dadf936 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -58,6 +58,7 @@ from django.utils.translation.reloader import (
translation_file_changed,
watch_for_translation_changes,
)
+from django.utils.translation.trans_real import LANGUAGE_CODE_MAX_LENGTH
from .forms import CompanyForm, I18nForm, SelectDateForm
from .models import Company, TestModel
@@ -1672,6 +1673,16 @@ class MiscTests(SimpleTestCase):
g("xyz")
with self.assertRaises(LookupError):
g("xy-zz")
+ msg = "'lang_code' exceeds the maximum accepted length"
+ with self.assertRaises(LookupError):
+ g("x" * LANGUAGE_CODE_MAX_LENGTH)
+ with self.assertRaisesMessage(ValueError, msg):
+ g("x" * (LANGUAGE_CODE_MAX_LENGTH + 1))
+ # 167 * 3 = 501 which is LANGUAGE_CODE_MAX_LENGTH + 1.
+ self.assertEqual(g("en-" * 167), "en")
+ with self.assertRaisesMessage(ValueError, msg):
+ g("en-" * 167, strict=True)
+ self.assertEqual(g("en-" * 30000), "en") # catastrophic test
def test_get_supported_language_variant_null(self):
g = trans_null.get_supported_language_variant