File CVE-2025-6075-expandvars-perf-degrad.patch of Package python.41898
From 8b8e68d3dc95f454f58fdd8aac10848facb1491d Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Fri, 31 Oct 2025 15:49:51 +0200
Subject: [PATCH 1/2] [3.9] gh-136065: Fix quadratic complexity in
os.path.expandvars() (GH-134952) (cherry picked from commit
f029e8db626ddc6e3a3beea4eff511a71aaceb5c)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
---
Lib/ntpath.py | 109 +++-------
Lib/posixpath.py | 39 +--
Lib/test/test_genericpath.py | 13 +
Lib/test/test_ntpath.py | 13 +
Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst | 1
5 files changed, 90 insertions(+), 85 deletions(-)
create mode 100644 Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst
Index: Python-2.7.18/Lib/ntpath.py
===================================================================
--- Python-2.7.18.orig/Lib/ntpath.py 2020-04-19 23:13:39.000000000 +0200
+++ Python-2.7.18/Lib/ntpath.py 2025-11-28 16:34:38.168313364 +0100
@@ -324,6 +324,10 @@
# XXX With COMMAND.COM you can use any characters in a variable name,
# XXX except '^|<>='.
+_varpattern = r"'[^']*'?|%(%|[^%]*%?)|\$(\$|[-\w]+|\{[^}]*\}?)"
+_varsub = None
+_varsubb = None
+
def expandvars(path):
"""Expand shell variables of the forms $var, ${var} and %var%.
@@ -331,7 +335,16 @@
if '$' not in path and '%' not in path:
return path
import string
- varchars = string.ascii_letters + string.digits + '_-'
+ if not _varsubb:
+ import re
+ _varsubb = re.compile(_varpattern.encode(), re.ASCII).sub
+ sub = _varsubb
+ percent = b'%'
+ brace = b'{'
+ rbrace = b'}'
+ dollar = b'$'
+ environ = getattr(os, 'environb', None)
+
if isinstance(path, _unicode):
encoding = sys.getfilesystemencoding()
def getenv(var):
@@ -339,73 +352,35 @@
else:
def getenv(var):
return os.environ[var]
- res = ''
- index = 0
- pathlen = len(path)
- while index < pathlen:
- c = path[index]
- if c == '\'': # no expansion within single quotes
- path = path[index + 1:]
- pathlen = len(path)
- try:
- index = path.index('\'')
- res = res + '\'' + path[:index + 1]
- except ValueError:
- res = res + c + path
- index = pathlen - 1
- elif c == '%': # variable or '%'
- if path[index + 1:index + 2] == '%':
- res = res + c
- index = index + 1
- else:
- path = path[index+1:]
- pathlen = len(path)
- try:
- index = path.index('%')
- except ValueError:
- res = res + '%' + path
- index = pathlen - 1
- else:
- var = path[:index]
- try:
- res = res + getenv(var)
- except KeyError:
- res = res + '%' + var + '%'
- elif c == '$': # variable or '$$'
- if path[index + 1:index + 2] == '$':
- res = res + c
- index = index + 1
- elif path[index + 1:index + 2] == '{':
- path = path[index+2:]
- pathlen = len(path)
- try:
- index = path.index('}')
- var = path[:index]
- try:
- res = res + getenv(var)
- except KeyError:
- res = res + '${' + var + '}'
- except ValueError:
- res = res + '${' + path
- index = pathlen - 1
- else:
- var = ''
- index = index + 1
- c = path[index:index + 1]
- while c != '' and c in varchars:
- var = var + c
- index = index + 1
- c = path[index:index + 1]
- try:
- res = res + getenv(var)
- except KeyError:
- res = res + '$' + var
- if c != '':
- index = index - 1
+
+ def repl(m):
+ lastindex = m.lastindex
+ if lastindex is None:
+ return m.group(0)
+ name = m.group(lastindex)
+ if lastindex == 1:
+ if name == percent:
+ return name
+ if not name.endswith(percent):
+ return m.group(0)
+ name = name[:-1]
else:
- res = res + c
- index = index + 1
- return res
+ if name == dollar:
+ return name
+ if name.startswith(brace):
+ if not name.endswith(rbrace):
+ return m.group(0)
+ name = name[1:-1]
+
+ try:
+ if environ is None:
+ return os.fsencode(os.environ[os.fsdecode(name)])
+ else:
+ return environ[name]
+ except KeyError:
+ return m.group(0)
+
+ return sub(repl, path)
# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A\B.
Index: Python-2.7.18/Lib/posixpath.py
===================================================================
--- Python-2.7.18.orig/Lib/posixpath.py 2020-04-19 23:13:39.000000000 +0200
+++ Python-2.7.18/Lib/posixpath.py 2025-11-28 17:02:18.835876821 +0100
@@ -284,35 +284,37 @@
# This expands the forms $variable and ${variable} only.
# Non-existent variables are left unchanged.
-_varprog = None
-_uvarprog = None
+_varpattern = r'\$(\w+|\{[^}]*\}?)'
+_varsub = None
+_varsubb = None
def expandvars(path):
"""Expand shell variables of form $var and ${var}. Unknown variables
are left unchanged."""
- global _varprog, _uvarprog
+ global _varsub, _varsubb
if '$' not in path:
return path
if isinstance(path, _unicode):
- if not _uvarprog:
+ if not _varsubb:
import re
- _uvarprog = re.compile(ur'\$(\w+|\{[^}]*\})', re.UNICODE)
- varprog = _uvarprog
+ _varsubb = re.compile(_varpattern.encode(), re.ASCII).sub
+ sub = _varsubb
encoding = sys.getfilesystemencoding()
else:
- if not _varprog:
+ if not _varsub:
import re
- _varprog = re.compile(r'\$(\w+|\{[^}]*\})')
- varprog = _varprog
+ _varsub = re.compile(_varpattern, re.ASCII).sub
+ sub = _varsub
encoding = None
- i = 0
- while True:
- m = varprog.search(path, i)
- if not m:
- break
- i, j = m.span(0)
+ start = '{'
+ end = '}'
+ environ = os.environ
+
+ def repl(m):
name = m.group(1)
- if name.startswith('{') and name.endswith('}'):
+ if name.startswith(start):
+ if not name.endswith(end):
+ return m.group(0)
name = name[1:-1]
if encoding:
name = name.encode(encoding)
@@ -325,8 +327,9 @@
i = len(path)
path += tail
else:
- i = j
- return path
+ return m.group(0)
+
+ return sub(repl, path)
# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B.
Index: Python-2.7.18/Lib/test/test_genericpath.py
===================================================================
--- Python-2.7.18.orig/Lib/test/test_genericpath.py 2020-04-19 23:13:39.000000000 +0200
+++ Python-2.7.18/Lib/test/test_genericpath.py 2025-11-28 16:21:35.651726913 +0100
@@ -233,6 +233,19 @@
check(u'$bar%s bar' % unonascii, u'$bar%s bar' % unonascii)
check(u'$spam}bar', u'%s}bar' % unonascii)
+ @support.requires_resource('cpu')
+ def test_expandvars_large(self):
+ expandvars = self.pathmodule.expandvars
+ with EnvironmentVarGuard() as env:
+ env.clear()
+ env["A"] = "B"
+ n = 100000
+ self.assertEqual(expandvars('$A'*n), 'B'*n)
+ self.assertEqual(expandvars('${A}'*n), 'B'*n)
+ self.assertEqual(expandvars('$A!'*n), 'B!'*n)
+ self.assertEqual(expandvars('${A}A'*n), 'BA'*n)
+ self.assertEqual(expandvars('${'*10*n), '${'*10*n)
+
def test_abspath(self):
self.assertIn("foo", self.pathmodule.abspath("foo"))
Index: Python-2.7.18/Lib/test/test_ntpath.py
===================================================================
--- Python-2.7.18.orig/Lib/test/test_ntpath.py 2020-04-19 23:13:39.000000000 +0200
+++ Python-2.7.18/Lib/test/test_ntpath.py 2025-11-28 16:25:10.488811010 +0100
@@ -232,6 +232,19 @@
check('%spam%bar', '%sbar' % snonascii)
check('%{}%bar'.format(snonascii), 'ham%sbar' % snonascii)
+ @support.requires_resource('cpu')
+ def test_expandvars_large(self):
+ expandvars = ntpath.expandvars
+ with test_support.EnvironmentVarGuard() as env:
+ env.clear()
+ env["A"] = "B"
+ n = 100000
+ self.assertEqual(expandvars('%A%'*n), 'B'*n)
+ self.assertEqual(expandvars('%A%A'*n), 'BA'*n)
+ self.assertEqual(expandvars("''"*n + '%%'), "''"*n + '%')
+ self.assertEqual(expandvars("%%"*n), "%"*n)
+ self.assertEqual(expandvars("$$"*n), "$"*n)
+
def test_expanduser(self):
tester('ntpath.expanduser("test")', 'test')
Index: Python-2.7.18/Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ Python-2.7.18/Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst 2025-11-28 16:21:35.652331536 +0100
@@ -0,0 +1 @@
+Fix quadratic complexity in :func:`os.path.expandvars`.
