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[3.14] gh-143921: Reject NUL, CR and LF in IMAP commands (GH-143922, GH-153067) #153137

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[3.14] gh-143921: Reject NUL, CR and LF in IMAP commands (GH-143922, GH-153067) #153137

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5 changes: 5 additions & 0 deletions Lib/imaplib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,9 @@
# We compile these in _mode_xxx.
_Literal = br'.*{(?P<size>\d+)}$'
_Untagged_status = br'\* (?P<data>\d+) (?P<type>[A-Z-]+)( (?P<data2>.*))?'
# Only NUL, CR and LF are unsafe (they cannot be represented even in
# a quoted string); other control characters are sent quoted.
_control_chars = re.compile(b'[\x00\r\n]')
_non_astring_char = re.compile(br'[(){ \x00-\x1f\x7f-\xff%*\\"]')
_non_list_char = re.compile(br'[(){ \x00-\x1f\x7f-\xff\\"]')
_quoted = re.compile(br'"(?:[^"\\]|\\.)*+"')
Expand Down Expand Up @@ -1155,6 +1158,8 @@ def _command(self, name, *args):
if arg is None: continue
if isinstance(arg, str):
arg = bytes(arg, self._encoding)
if _control_chars.search(arg):
raise ValueError("NUL, CR and LF not allowed in commands")
data = data + b' ' + arg

literal = self.literal
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16 changes: 16 additions & 0 deletions Lib/test/test_imaplib.py
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Expand Up @@ -1741,6 +1741,22 @@ def test_uppercase_command_names(self):
with self.assertRaises(AttributeError):
client.NONEXISTENT

def test_control_characters(self):
client, server = self._setup(SimpleIMAPHandler)
client.login('user', 'pass')
for c in '\0\r\n':
with self.assertRaises(ValueError):
client.select(f'a{c}b')
# Other control characters are valid in a quoted string and can
# occur in mailbox names returned by the server, so the client
# must be able to send them back.
for c in support.control_characters_c0():
if c in '\0\r\n':
continue
typ, _ = client.select(f'a{c}b')
self.assertEqual(typ, 'OK')
self.assertEqual(server.is_selected, [f'"a{c}b"'])

# property tests

def test_file_property_should_not_be_accessed(self):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Security/2026-01-16-11-41-06.gh-issue-143921.AeCOor.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Reject NUL, CR and LF characters in IMAP commands. Other control
characters are allowed and sent quoted.
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