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gh-150479: reject CR and LF in email.utils.formataddr #150480

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gh-150479: reject CR and LF in email.utils.formataddr #150480

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2 changes: 2 additions & 0 deletions Lib/email/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,8 @@ def formataddr(pair, charset='utf-8'):
'utf-8'.
"""
name, address = pair
if '\r' in address or '\n' in address or (name and ('\r' in name or '\n' in name)):
raise ValueError("invalid arguments; address parts cannot contain CR or LF")
# The address MUST (per RFC) be ascii, so raise a UnicodeError if it isn't.
address.encode('ascii')
if name:
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13 changes: 13 additions & 0 deletions Lib/test/test_email/test_email.py
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Expand Up @@ -3277,6 +3277,19 @@ def test_unicode_address_raises_error(self):
self.assertRaises(UnicodeError, utils.formataddr, (None, addr))
self.assertRaises(UnicodeError, utils.formataddr, ("Name", addr))

def test_crlf_in_parts_raises_error(self):
# formataddr() must reject CR and LF in either part so that the
# returned header value cannot be used to inject extra headers,
# matching email.headerregistry.Address.
for name, addr in [
('Real\rName', 'person@dom.ain'),
('Real\nName', 'person@dom.ain'),
('Real Name', 'person@dom.ain\r\nBcc: victim@dom.ain'),
('Real Name', 'person@dom.ain\nSubject: spoofed'),
]:
with self.subTest(name=name, addr=addr):
self.assertRaises(ValueError, utils.formataddr, (name, addr))

def test_name_with_dot(self):
x = 'John X. Doe <jxd@example.com>'
y = '"John X. Doe" <jxd@example.com>'
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Security/2026-05-26-19-30-00.gh-issue-150479.Kq7Lm2.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
:func:`email.utils.formataddr` now raises :exc:`ValueError` when the name or
address contains a carriage return or line feed, preventing header injection
and matching :class:`email.headerregistry.Address`.
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