[3.11] gh-146333: Fix quadratic regex backtracking in configparser option parsing (GH-146399) (GH-148559) (GH-154081) by miss-islington · Pull Request #155160 · python/cpython · GitHub
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[3.11] gh-146333: Fix quadratic regex backtracking in configparser option parsing (GH-146399) (GH-148559) (GH-154081) #155160

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[3.11] gh-146333: Fix quadratic regex backtracking in configparser option parsing (GH-146399) (GH-148559) (GH-154081) #155160

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8 changes: 6 additions & 2 deletions Lib/configparser.py
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20 changes: 20 additions & 0 deletions Lib/test/test_configparser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2166,6 +2166,26 @@ def test_instance_assignment(self):
self.assertEqual(cfg['two'].getlen('one'), 5)


class ReDoSTestCase(unittest.TestCase):
"""Regression tests for quadratic regex backtracking (gh-146333)."""

def test_option_regex_does_not_backtrack(self):
# A line with many spaces between non-delimiter characters
# should be parsed in linear time, not quadratic.
parser = configparser.RawConfigParser()
content = "[section]\n" + "x" + " " * 40000 + "y" + "\n"
# This should complete almost instantly. Before the fix,
# it would take over a minute due to catastrophic backtracking.
with self.assertRaises(configparser.ParsingError):
parser.read_string(content)

def test_option_regex_no_value_does_not_backtrack(self):
parser = configparser.RawConfigParser(allow_no_value=True)
content = "[section]\n" + "x" + " " * 40000 + "y" + "\n"
parser.read_string(content)
self.assertTrue(parser.has_option("section", "x" + " " * 40000 + "y"))


class MiscTestCase(unittest.TestCase):
def test__all__(self):
support.check__all__(self, configparser, not_exported={"Error"})
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Security/2026-03-25-00-51-03.gh-issue-146333.LqdL__bn.rst
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