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escape attachment filename in Content-Disposition header #69435

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Merged
potiuk merged 1 commit into from
Jul 31, 2026
Merged

escape attachment filename in Content-Disposition header #69435

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2 changes: 1 addition & 1 deletion airflow-core/src/airflow/utils/email.py
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Original file line number Diff line number Diff line change
Expand Up @@ -208,7 +208,7 @@ def build_mime_message(
basename = os.path.basename(fname)
with open(fname, "rb") as file:
part = MIMEApplication(file.read(), Name=basename)
part["Content-Disposition"] = f'attachment; filename="{basename}"'
part.add_header("Content-Disposition", "attachment", filename=basename)
part["Content-ID"] = f"<{basename}>"
msg.attach(part)

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19 changes: 19 additions & 0 deletions airflow-core/tests/unit/utils/test_email.py
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,25 @@ def test_build_mime_message(self):
assert [mail_to] == recipients
assert msg["To"] == ",".join(recipients)

def test_build_mime_message_escapes_attachment_filename(self, tmp_path):
# A quote in the filename must not break out of the quoted
# Content-Disposition value and inject extra parameters.
malicious = 'report.txt"; x-evil="1'
attachment = tmp_path / malicious
attachment.write_bytes(b"data")

msg, _ = email.build_mime_message(
mail_from="from@example.com",
to="to@example.com",
subject="subject",
html_content="<html></html>",
files=[os.fspath(attachment)],
)

part = msg.get_payload()[-1]
assert part.get_filename() == malicious
assert "x-evil" not in dict(part.get_params(header="Content-Disposition"))


@pytest.mark.db_test
class TestEmailSmtp:
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2 changes: 1 addition & 1 deletion providers/smtp/src/airflow/providers/smtp/hooks/smtp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -573,7 +573,7 @@ def _build_mime_message(
basename = os.path.basename(fname)
with open(fname, "rb") as file:
part = MIMEApplication(file.read(), Name=basename)
part["Content-Disposition"] = f'attachment; filename="{basename}"'
part.add_header("Content-Disposition", "attachment", filename=basename)
part["Content-ID"] = f"<{basename}>"
msg.attach(part)

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20 changes: 20 additions & 0 deletions providers/smtp/tests/unit/smtp/hooks/test_smtp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -235,6 +235,26 @@ def test_build_mime_message(self, mock_smtplib):
assert [mail_to] == recipients
assert msg["To"] == ",".join(recipients)

@patch(smtplib_string)
def test_build_mime_message_escapes_attachment_filename(self, mock_smtplib, tmp_path):
# A quote in the filename must not break out of the quoted
# Content-Disposition value and inject extra parameters.
malicious = 'report.txt"; x-evil="1'
attachment = tmp_path / malicious
attachment.write_bytes(b"data")
with SmtpHook() as smtp_hook:
msg, _ = smtp_hook._build_mime_message(
mail_from=FROM_EMAIL,
to=TO_EMAIL,
subject=TEST_SUBJECT,
html_content=TEST_BODY,
files=[os.fspath(attachment)],
)

part = msg.get_payload()[-1]
assert part.get_filename() == malicious
assert "x-evil" not in dict(part.get_params(header="Content-Disposition"))

@patch(smtplib_string)
def test_send_smtp(self, mock_smtplib):
mock_send_mime = mock_smtplib.SMTP_SSL().sendmail
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