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[2.0.x] Fixed CVE-2019-6975 -- Fixed memory exhaustion in utils.numbe…

…rformat.format().

Thanks Sjoerd Job Postmus for the report and initial patch.
Thanks Michael Manfre, Tim Graham, and Florian Apolloner for review.
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carltongibson committed Feb 11, 2019
1 parent f6f0f52 commit 1f42f82566c9d2d73aff1c42790d6b1b243f7676
Showing with 57 additions and 1 deletion.
  1. +14 −1 django/utils/numberformat.py
  2. +12 −0 docs/releases/1.11.19.txt
  3. +12 −0 docs/releases/2.0.11.txt
  4. +19 −0 tests/utils_tests/test_numberformat.py
@@ -27,7 +27,20 @@ def format(number, decimal_sep, decimal_pos=None, grouping=0, thousand_sep='',
# sign
sign = ''
if isinstance(number, Decimal):
str_number = '{:f}'.format(number)
# Format values with more than 200 digits (an arbitrary cutoff) using
# scientific notation to avoid high memory usage in {:f}'.format().
_, digits, exponent = number.as_tuple()
if abs(exponent) + len(digits) > 200:
number = '{:e}'.format(number)
coefficient, exponent = number.split('e')
# Format the coefficient.
coefficient = format(
coefficient, decimal_sep, decimal_pos, grouping,
thousand_sep, force_grouping, use_l10n,
)
return '{}e{}'.format(coefficient, exponent)
else:
str_number = '{:f}'.format(number)
else:
str_number = str(number)
if str_number[0] == '-':
@@ -5,3 +5,15 @@ Django 1.11.19 release notes
*February 11, 2019*

Django 1.11.19 fixes a security issue in 1.11.18.

CVE-2019-6975: Memory exhaustion in ``django.utils.numberformat.format()``
--------------------------------------------------------------------------

If ``django.utils.numberformat.format()`` -- used by ``contrib.admin`` as well
as the the ``floatformat``, ``filesizeformat``, and ``intcomma`` templates
filters -- received a ``Decimal`` with a large number of digits or a large
exponent, it could lead to significant memory usage due to a call to
``'{:f}'.format()``.

To avoid this, decimals with more than 200 digits are now formatted using
scientific notation.
@@ -5,3 +5,15 @@ Django 2.0.11 release notes
*February 11, 2019*

Django 2.0.11 fixes a security issue in 2.0.10.

CVE-2019-6975: Memory exhaustion in ``django.utils.numberformat.format()``
--------------------------------------------------------------------------

If ``django.utils.numberformat.format()`` -- used by ``contrib.admin`` as well
as the the ``floatformat``, ``filesizeformat``, and ``intcomma`` templates
filters -- received a ``Decimal`` with a large number of digits or a large
exponent, it could lead to significant memory usage due to a call to
``'{:f}'.format()``.

To avoid this, decimals with more than 200 digits are now formatted using
scientific notation.
@@ -75,6 +75,25 @@ def test_decimal_numbers(self):
)
self.assertEqual(nformat(Decimal('3.'), '.'), '3')
self.assertEqual(nformat(Decimal('3.0'), '.'), '3.0')
# Very large & small numbers.
tests = [
('9e9999', None, '9e+9999'),
('9e9999', 3, '9.000e+9999'),
('9e201', None, '9e+201'),
('9e200', None, '9e+200'),
('1.2345e999', 2, '1.23e+999'),
('9e-999', None, '9e-999'),
('1e-7', 8, '0.00000010'),
('1e-8', 8, '0.00000001'),
('1e-9', 8, '0.00000000'),
('1e-10', 8, '0.00000000'),
('1e-11', 8, '0.00000000'),
('1' + ('0' * 300), 3, '1.000e+300'),
('0.{}1234'.format('0' * 299), 3, '1.234e-300'),
]
for value, decimal_pos, expected_value in tests:
with self.subTest(value=value):
self.assertEqual(nformat(Decimal(value), '.', decimal_pos), expected_value)

def test_decimal_subclass(self):
class EuroDecimal(Decimal):

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