python3: fix CVE-2021-23336

The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before
3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable
to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by
using a vector called parameter cloaking. When the attacker can separate query
parameters using a semicolon (;), they can cause a difference in the
interpretation of the request between the proxy (running with default
configuration) and the server. This can result in malicious requests being
cached as completely safe ones, as the proxy would usually not see the
semicolon as a separator, and therefore would not include it in a cache key of
an unkeyed parameter.

References:
https://nvd.nist.gov/vuln/detail/CVE-2021-23336
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23336

(From OE-Core rev: 8a59c47ce4c101b2470a06ecf101ca5ab7d1f82e)

Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com>
Signed-off-by: Tim Orling <timothy.t.orling@intel.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 531 insertions, 0 deletions

diff --git a/meta/recipes-devtools/python/python3/CVE-2021-23336.patch b/meta/recipes-devtools/python/python3/CVE-2021-23336.patch
new file mode 100644
index 0000000000..2a885b9d37
--- /dev/null
+++ b/meta/recipes-devtools/python/python3/CVE-2021-23336.patch
@@ -0,0 +1,530 @@
+From 3ab6f812653e79d008d5eba31dc25d34f3ca7170 Mon Sep 17 00:00:00 2001
+From: Senthil Kumaran <senthil@uthcode.com>
+Date: Mon, 15 Feb 2021 10:15:02 -0800
+Subject: [PATCH] bpo-42967: only use '&' as a query string separator
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+ (GH-24297)  (#24529)
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+* bpo-42967: only use '&' as a query string separator (#24297)
+
+bpo-42967: [security] Address a web cache-poisoning issue reported in
+urllib.parse.parse_qsl().
+
+urllib.parse will only us "&" as query string separator by default
+instead of both ";" and "&" as allowed in earlier versions. An optional
+argument seperator with default value "&" is added to specify the
+separator.
+
+Co-authored-by: Éric Araujo <merwok@netwok.org>
+Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
+Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
+Co-authored-by: Éric Araujo <merwok@netwok.org>
+(cherry picked from commit fcbe0cb04d35189401c0c880ebfb4311e952d776)
+
+* [3.8] bpo-42967: only use '&' as a query string separator (GH-24297)
+
+bpo-42967: [security] Address a web cache-poisoning issue reported in urllib.parse.parse_qsl().
+
+urllib.parse will only us "&" as query string separator by default instead of both ";" and "&" as allowed in earlier versions. An optional argument seperator with default value "&" is added to specify the separator.
+
+Co-authored-by: Éric Araujo <merwok@netwok.org>
+Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
+Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
+Co-authored-by: Éric Araujo <merwok@netwok.org>.
+(cherry picked from commit fcbe0cb04d35189401c0c880ebfb4311e952d776)
+
+Co-authored-by: Adam Goldschmidt <adamgold7@gmail.com>
+
+* Update correct version information.
+
+* fix docs and make logic clearer
+
+Co-authored-by: Adam Goldschmidt <adamgold7@gmail.com>
+Co-authored-by: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
+
+Upstream-Status: Backport [https://github.com/python/cpython/commit/e3110c3cfbb7daa690d54d0eff6c264c870a71bf]
+CVE: CVE-2020-23336
+Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com>
+
+---
+ Doc/library/cgi.rst                           | 11 ++-
+ Doc/library/urllib.parse.rst                  | 22 +++++-
+ Doc/whatsnew/3.6.rst                          | 13 ++++
+ Doc/whatsnew/3.7.rst                          | 13 ++++
+ Lib/cgi.py                                    | 23 ++++---
+ Lib/test/test_cgi.py                          | 29 ++++++--
+ Lib/test/test_urlparse.py                     | 68 +++++++++++++------
+ Lib/urllib/parse.py                           | 19 ++++--
+ .../2021-02-14-15-59-16.bpo-42967.YApqDS.rst  |  1 +
+ 9 files changed, 153 insertions(+), 46 deletions(-)
+ create mode 100644 Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
+
+diff --git a/Doc/library/cgi.rst b/Doc/library/cgi.rst
+index 4048592..880074b 100644
+--- a/Doc/library/cgi.rst
++++ b/Doc/library/cgi.rst
+@@ -277,14 +277,16 @@ These are useful if you want more control, or if you want to employ some of the
+ algorithms implemented in this module in other circumstances.
+ 
+ 
+-.. function:: parse(fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False)
++.. function:: parse(fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False, separator="&")
+ 
+    Parse a query in the environment or from a file (the file defaults to
+-   ``sys.stdin``).  The *keep_blank_values* and *strict_parsing* parameters are
++   ``sys.stdin``).  The *keep_blank_values*, *strict_parsing* and *separator* parameters are
+    passed to :func:`urllib.parse.parse_qs` unchanged.
+ 
++   .. versionchanged:: 3.8.8
++      Added the *separator* parameter.
+ 
+-.. function:: parse_multipart(fp, pdict, encoding="utf-8", errors="replace")
++.. function:: parse_multipart(fp, pdict, encoding="utf-8", errors="replace", separator="&")
+ 
+    Parse input of type :mimetype:`multipart/form-data` (for  file uploads).
+    Arguments are *fp* for the input file, *pdict* for a dictionary containing
+@@ -303,6 +305,9 @@ algorithms implemented in this module in other circumstances.
+       Added the *encoding* and *errors* parameters.  For non-file fields, the
+       value is now a list of strings, not bytes.
+ 
++   .. versionchanged:: 3.8.8
++      Added the *separator* parameter.
++
+ 
+ .. function:: parse_header(string)
+ 
+diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst
+index 52f98ef..45ca03a 100644
+--- a/Doc/library/urllib.parse.rst
++++ b/Doc/library/urllib.parse.rst
+@@ -165,7 +165,7 @@ or on combining URL components into a URL string.
+       now raise :exc:`ValueError`.
+ 
+ 
+-.. function:: parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)
++.. function:: parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')
+ 
+    Parse a query string given as a string argument (data of type
+    :mimetype:`application/x-www-form-urlencoded`).  Data are returned as a
+@@ -190,6 +190,9 @@ or on combining URL components into a URL string.
+    read. If set, then throws a :exc:`ValueError` if there are more than
+    *max_num_fields* fields read.
+ 
++   The optional argument *separator* is the symbol to use for separating the
++   query arguments. It defaults to ``&``.
++
+    Use the :func:`urllib.parse.urlencode` function (with the ``doseq``
+    parameter set to ``True``) to convert such dictionaries into query
+    strings.
+@@ -201,8 +204,14 @@ or on combining URL components into a URL string.
+    .. versionchanged:: 3.8
+       Added *max_num_fields* parameter.
+ 
++   .. versionchanged:: 3.8.8
++      Added *separator* parameter with the default value of ``&``. Python
++      versions earlier than Python 3.8.8 allowed using both ``;`` and ``&`` as
++      query parameter separator. This has been changed to allow only a single
++      separator key, with ``&`` as the default separator.
++
+ 
+-.. function:: parse_qsl(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)
++.. function:: parse_qsl(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')
+ 
+    Parse a query string given as a string argument (data of type
+    :mimetype:`application/x-www-form-urlencoded`).  Data are returned as a list of
+@@ -226,6 +235,9 @@ or on combining URL components into a URL string.
+    read. If set, then throws a :exc:`ValueError` if there are more than
+    *max_num_fields* fields read.
+ 
++   The optional argument *separator* is the symbol to use for separating the
++   query arguments. It defaults to ``&``.
++
+    Use the :func:`urllib.parse.urlencode` function to convert such lists of pairs into
+    query strings.
+ 
+@@ -235,6 +247,12 @@ or on combining URL components into a URL string.
+    .. versionchanged:: 3.8
+       Added *max_num_fields* parameter.
+ 
++   .. versionchanged:: 3.8.8
++      Added *separator* parameter with the default value of ``&``. Python
++      versions earlier than Python 3.8.8 allowed using both ``;`` and ``&`` as
++      query parameter separator. This has been changed to allow only a single
++      separator key, with ``&`` as the default separator.
++
+ 
+ .. function:: urlunparse(parts)
+ 
+diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
+index 04c1f7e..4409a3a 100644
+--- a/Doc/whatsnew/3.6.rst
++++ b/Doc/whatsnew/3.6.rst
+@@ -2443,3 +2443,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
+ details, see the documentation for ``loop.create_datagram_endpoint()``.
+ (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
+ :issue:`37228`.)
++
++Notable changes in Python 3.6.13
++================================
++
++Earlier Python versions allowed using both ``;`` and ``&`` as
++query parameter separators in :func:`urllib.parse.parse_qs` and
++:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
++newer W3C recommendations, this has been changed to allow only a single
++separator key, with ``&`` as the default.  This change also affects
++:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
++functions internally. For more details, please see their respective
++documentation.
++(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
+diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
+index b9b5021..8f47a9f 100644
+--- a/Doc/whatsnew/3.7.rst
++++ b/Doc/whatsnew/3.7.rst
+@@ -2556,3 +2556,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
+ details, see the documentation for ``loop.create_datagram_endpoint()``.
+ (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
+ :issue:`37228`.)
++
++Notable changes in Python 3.7.10
++================================
++
++Earlier Python versions allowed using both ``;`` and ``&`` as
++query parameter separators in :func:`urllib.parse.parse_qs` and
++:func:`urllib.parse.parse_qsl`.  Due to security concerns, and to conform with
++newer W3C recommendations, this has been changed to allow only a single
++separator key, with ``&`` as the default.  This change also affects
++:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
++functions internally. For more details, please see their respective
++documentation.
++(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
+diff --git a/Lib/cgi.py b/Lib/cgi.py
+index 5ace46a..13255a9 100755
+--- a/Lib/cgi.py
++++ b/Lib/cgi.py
+@@ -106,7 +106,8 @@ log = initlog           # The current logging function
+ # 0 ==> unlimited input
+ maxlen = 0
+ 
+-def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
++def parse(fp=None, environ=os.environ, keep_blank_values=0,
++          strict_parsing=0, separator='&'):
+     """Parse a query in the environment or from a file (default stdin)
+ 
+         Arguments, all optional:
+@@ -125,6 +126,9 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
+         strict_parsing: flag indicating what to do with parsing errors.
+             If false (the default), errors are silently ignored.
+             If true, errors raise a ValueError exception.
++
++        separator: str. The symbol to use for separating the query arguments.
++            Defaults to &.
+     """
+     if fp is None:
+         fp = sys.stdin
+@@ -145,7 +149,7 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
+     if environ['REQUEST_METHOD'] == 'POST':
+         ctype, pdict = parse_header(environ['CONTENT_TYPE'])
+         if ctype == 'multipart/form-data':
+-            return parse_multipart(fp, pdict)
++            return parse_multipart(fp, pdict, separator=separator)
+         elif ctype == 'application/x-www-form-urlencoded':
+             clength = int(environ['CONTENT_LENGTH'])
+             if maxlen and clength > maxlen:
+@@ -169,10 +173,10 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
+             qs = ""
+         environ['QUERY_STRING'] = qs    # XXX Shouldn't, really
+     return urllib.parse.parse_qs(qs, keep_blank_values, strict_parsing,
+-                                 encoding=encoding)
++                                 encoding=encoding, separator=separator)
+ 
+ 
+-def parse_multipart(fp, pdict, encoding="utf-8", errors="replace"):
++def parse_multipart(fp, pdict, encoding="utf-8", errors="replace", separator='&'):
+     """Parse multipart input.
+ 
+     Arguments:
+@@ -193,7 +197,7 @@ def parse_multipart(fp, pdict, encoding="utf-8", errors="replace"):
+     headers.set_type(ctype)
+     headers['Content-Length'] = pdict['CONTENT-LENGTH']
+     fs = FieldStorage(fp, headers=headers, encoding=encoding, errors=errors,
+-        environ={'REQUEST_METHOD': 'POST'})
++        environ={'REQUEST_METHOD': 'POST'}, separator=separator)
+     return {k: fs.getlist(k) for k in fs}
+ 
+ def _parseparam(s):
+@@ -303,7 +307,7 @@ class FieldStorage:
+     def __init__(self, fp=None, headers=None, outerboundary=b'',
+                  environ=os.environ, keep_blank_values=0, strict_parsing=0,
+                  limit=None, encoding='utf-8', errors='replace',
+-                 max_num_fields=None):
++                 max_num_fields=None, separator='&'):
+         """Constructor.  Read multipart/* until last part.
+ 
+         Arguments, all optional:
+@@ -351,6 +355,7 @@ class FieldStorage:
+         self.keep_blank_values = keep_blank_values
+         self.strict_parsing = strict_parsing
+         self.max_num_fields = max_num_fields
++        self.separator = separator
+         if 'REQUEST_METHOD' in environ:
+             method = environ['REQUEST_METHOD'].upper()
+         self.qs_on_post = None
+@@ -577,7 +582,7 @@ class FieldStorage:
+         query = urllib.parse.parse_qsl(
+             qs, self.keep_blank_values, self.strict_parsing,
+             encoding=self.encoding, errors=self.errors,
+-            max_num_fields=self.max_num_fields)
++            max_num_fields=self.max_num_fields, separator=self.separator)
+         self.list = [MiniFieldStorage(key, value) for key, value in query]
+         self.skip_lines()
+ 
+@@ -593,7 +598,7 @@ class FieldStorage:
+             query = urllib.parse.parse_qsl(
+                 self.qs_on_post, self.keep_blank_values, self.strict_parsing,
+                 encoding=self.encoding, errors=self.errors,
+-                max_num_fields=self.max_num_fields)
++                max_num_fields=self.max_num_fields, separator=self.separator)
+             self.list.extend(MiniFieldStorage(key, value) for key, value in query)
+ 
+         klass = self.FieldStorageClass or self.__class__
+@@ -637,7 +642,7 @@ class FieldStorage:
+                 else self.limit - self.bytes_read
+             part = klass(self.fp, headers, ib, environ, keep_blank_values,
+                          strict_parsing, limit,
+-                         self.encoding, self.errors, max_num_fields)
++                         self.encoding, self.errors, max_num_fields, self.separator)
+ 
+             if max_num_fields is not None:
+                 max_num_fields -= 1
+diff --git a/Lib/test/test_cgi.py b/Lib/test/test_cgi.py
+index ab86771..bda03ee 100644
+--- a/Lib/test/test_cgi.py
++++ b/Lib/test/test_cgi.py
+@@ -53,12 +53,9 @@ parse_strict_test_cases = [
+     ("", ValueError("bad query field: ''")),
+     ("&", ValueError("bad query field: ''")),
+     ("&&", ValueError("bad query field: ''")),
+-    (";", ValueError("bad query field: ''")),
+-    (";&;", ValueError("bad query field: ''")),
+     # Should the next few really be valid?
+     ("=", {}),
+     ("=&=", {}),
+-    ("=;=", {}),
+     # This rest seem to make sense
+     ("=a", {'': ['a']}),
+     ("&=a", ValueError("bad query field: ''")),
+@@ -73,8 +70,6 @@ parse_strict_test_cases = [
+     ("a=a+b&b=b+c", {'a': ['a b'], 'b': ['b c']}),
+     ("a=a+b&a=b+a", {'a': ['a b', 'b a']}),
+     ("x=1&y=2.0&z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
+-    ("x=1;y=2.0&z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
+-    ("x=1;y=2.0;z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
+     ("Hbc5161168c542333633315dee1182227:key_store_seqid=400006&cuyer=r&view=bustomer&order_id=0bb2e248638833d48cb7fed300000f1b&expire=964546263&lobale=en-US&kid=130003.300038&ss=env",
+      {'Hbc5161168c542333633315dee1182227:key_store_seqid': ['400006'],
+       'cuyer': ['r'],
+@@ -187,6 +182,30 @@ Content-Length: 3
+                     else:
+                         self.assertEqual(fs.getvalue(key), expect_val[0])
+ 
++    def test_separator(self):
++        parse_semicolon = [
++            ("x=1;y=2.0", {'x': ['1'], 'y': ['2.0']}),
++            ("x=1;y=2.0;z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
++            (";", ValueError("bad query field: ''")),
++            (";;", ValueError("bad query field: ''")),
++            ("=;a", ValueError("bad query field: 'a'")),
++            (";b=a", ValueError("bad query field: ''")),
++            ("b;=a", ValueError("bad query field: 'b'")),
++            ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
++            ("a=a+b;a=b+a", {'a': ['a b', 'b a']}),
++        ]
++        for orig, expect in parse_semicolon:
++            env = {'QUERY_STRING': orig}
++            fs = cgi.FieldStorage(separator=';', environ=env)
++            if isinstance(expect, dict):
++                for key in expect.keys():
++                    expect_val = expect[key]
++                    self.assertIn(key, fs)
++                    if len(expect_val) > 1:
++                        self.assertEqual(fs.getvalue(key), expect_val)
++                    else:
++                        self.assertEqual(fs.getvalue(key), expect_val[0])
++
+     def test_log(self):
+         cgi.log("Testing")
+ 
+diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py
+index 4ae6ed3..90c8d69 100644
+--- a/Lib/test/test_urlparse.py
++++ b/Lib/test/test_urlparse.py
+@@ -32,16 +32,10 @@ parse_qsl_test_cases = [
+     (b"&a=b", [(b'a', b'b')]),
+     (b"a=a+b&b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
+     (b"a=1&a=2", [(b'a', b'1'), (b'a', b'2')]),
+-    (";", []),
+-    (";;", []),
+-    (";a=b", [('a', 'b')]),
+-    ("a=a+b;b=b+c", [('a', 'a b'), ('b', 'b c')]),
+-    ("a=1;a=2", [('a', '1'), ('a', '2')]),
+-    (b";", []),
+-    (b";;", []),
+-    (b";a=b", [(b'a', b'b')]),
+-    (b"a=a+b;b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
+-    (b"a=1;a=2", [(b'a', b'1'), (b'a', b'2')]),
++    (";a=b", [(';a', 'b')]),
++    ("a=a+b;b=b+c", [('a', 'a b;b=b c')]),
++    (b";a=b", [(b';a', b'b')]),
++    (b"a=a+b;b=b+c", [(b'a', b'a b;b=b c')]),
+ ]
+ 
+ # Each parse_qs testcase is a two-tuple that contains
+@@ -68,16 +62,10 @@ parse_qs_test_cases = [
+     (b"&a=b", {b'a': [b'b']}),
+     (b"a=a+b&b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
+     (b"a=1&a=2", {b'a': [b'1', b'2']}),
+-    (";", {}),
+-    (";;", {}),
+-    (";a=b", {'a': ['b']}),
+-    ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
+-    ("a=1;a=2", {'a': ['1', '2']}),
+-    (b";", {}),
+-    (b";;", {}),
+-    (b";a=b", {b'a': [b'b']}),
+-    (b"a=a+b;b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
+-    (b"a=1;a=2", {b'a': [b'1', b'2']}),
++    (";a=b", {';a': ['b']}),
++    ("a=a+b;b=b+c", {'a': ['a b;b=b c']}),
++    (b";a=b", {b';a': [b'b']}),
++    (b"a=a+b;b=b+c", {b'a':[ b'a b;b=b c']}),
+ ]
+ 
+ class UrlParseTestCase(unittest.TestCase):
+@@ -884,10 +872,46 @@ class UrlParseTestCase(unittest.TestCase):
+     def test_parse_qsl_max_num_fields(self):
+         with self.assertRaises(ValueError):
+             urllib.parse.parse_qs('&'.join(['a=a']*11), max_num_fields=10)
+-        with self.assertRaises(ValueError):
+-            urllib.parse.parse_qs(';'.join(['a=a']*11), max_num_fields=10)
+         urllib.parse.parse_qs('&'.join(['a=a']*10), max_num_fields=10)
+ 
++    def test_parse_qs_separator(self):
++        parse_qs_semicolon_cases = [
++            (";", {}),
++            (";;", {}),
++            (";a=b", {'a': ['b']}),
++            ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
++            ("a=1;a=2", {'a': ['1', '2']}),
++            (b";", {}),
++            (b";;", {}),
++            (b";a=b", {b'a': [b'b']}),
++            (b"a=a+b;b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
++            (b"a=1;a=2", {b'a': [b'1', b'2']}),
++        ]
++        for orig, expect in parse_qs_semicolon_cases:
++            with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
++                result = urllib.parse.parse_qs(orig, separator=';')
++                self.assertEqual(result, expect, "Error parsing %r" % orig)
++
++
++    def test_parse_qsl_separator(self):
++        parse_qsl_semicolon_cases = [
++            (";", []),
++            (";;", []),
++            (";a=b", [('a', 'b')]),
++            ("a=a+b;b=b+c", [('a', 'a b'), ('b', 'b c')]),
++            ("a=1;a=2", [('a', '1'), ('a', '2')]),
++            (b";", []),
++            (b";;", []),
++            (b";a=b", [(b'a', b'b')]),
++            (b"a=a+b;b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
++            (b"a=1;a=2", [(b'a', b'1'), (b'a', b'2')]),
++        ]
++        for orig, expect in parse_qsl_semicolon_cases:
++            with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
++                result = urllib.parse.parse_qsl(orig, separator=';')
++                self.assertEqual(result, expect, "Error parsing %r" % orig)
++
++
+     def test_urlencode_sequences(self):
+         # Other tests incidentally urlencode things; test non-covered cases:
+         # Sequence and object values.
+diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
+index e2b6f13..5a3e847 100644
+--- a/Lib/urllib/parse.py
++++ b/Lib/urllib/parse.py
+@@ -648,7 +648,7 @@ def unquote(string, encoding='utf-8', errors='replace'):
+ 
+ 
+ def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
+-             encoding='utf-8', errors='replace', max_num_fields=None):
++             encoding='utf-8', errors='replace', max_num_fields=None, separator='&'):
+     """Parse a query given as a string argument.
+ 
+         Arguments:
+@@ -672,12 +672,15 @@ def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
+         max_num_fields: int. If set, then throws a ValueError if there
+             are more than n fields read by parse_qsl().
+ 
++        separator: str. The symbol to use for separating the query arguments.
++            Defaults to &.
++
+         Returns a dictionary.
+     """
+     parsed_result = {}
+     pairs = parse_qsl(qs, keep_blank_values, strict_parsing,
+                       encoding=encoding, errors=errors,
+-                      max_num_fields=max_num_fields)
++                      max_num_fields=max_num_fields, separator=separator)
+     for name, value in pairs:
+         if name in parsed_result:
+             parsed_result[name].append(value)
+@@ -687,7 +690,7 @@ def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
+ 
+ 
+ def parse_qsl(qs, keep_blank_values=False, strict_parsing=False,
+-              encoding='utf-8', errors='replace', max_num_fields=None):
++              encoding='utf-8', errors='replace', max_num_fields=None, separator='&'):
+     """Parse a query given as a string argument.
+ 
+         Arguments:
+@@ -710,19 +713,25 @@ def parse_qsl(qs, keep_blank_values=False, strict_parsing=False,
+         max_num_fields: int. If set, then throws a ValueError
+             if there are more than n fields read by parse_qsl().
+ 
++        separator: str. The symbol to use for separating the query arguments.
++            Defaults to &.
++
+         Returns a list, as G-d intended.
+     """
+     qs, _coerce_result = _coerce_args(qs)
+ 
++    if not separator or (not isinstance(separator, (str, bytes))):
++        raise ValueError("Separator must be of type string or bytes.")
++
+     # If max_num_fields is defined then check that the number of fields
+     # is less than max_num_fields. This prevents a memory exhaustion DOS
+     # attack via post bodies with many fields.
+     if max_num_fields is not None:
+-        num_fields = 1 + qs.count('&') + qs.count(';')
++        num_fields = 1 + qs.count(separator)
+         if max_num_fields < num_fields:
+             raise ValueError('Max number of fields exceeded')
+ 
+-    pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')]
++    pairs = [s1 for s1 in qs.split(separator)]
+     r = []
+     for name_value in pairs:
+         if not name_value and not strict_parsing:
+diff --git a/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst b/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
+new file mode 100644
+index 0000000..f08489b
+--- /dev/null
++++ b/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
+@@ -0,0 +1 @@
++Fix web cache poisoning vulnerability by defaulting the query args separator to ``&``, and allowing the user to choose a custom separator.
diff --git a/meta/recipes-devtools/python/python3_3.8.2.bb b/meta/recipes-devtools/python/python3_3.8.2.bb
index 072ce97472..762e9444b8 100644
--- a/meta/recipes-devtools/python/python3_3.8.2.bb
+++ b/meta/recipes-devtools/python/python3_3.8.2.bb
@@ -39,6 +39,7 @@ SRC_URI = "http://www.python.org/ftp/python/${PV}/Python-${PV}.tar.xz \
            file://CVE-2020-26116.patch \
            file://CVE-2020-27619.patch \
            file://CVE-2021-3177.patch \
+           file://CVE-2021-23336.patch \
            "
 
 SRC_URI_append_class-native = " \