`TypeError: '<' not supported between instances of 'NoneType' and 'int'` raised during call to `email.message_from_file`

[gabe-sherman]

Bug report

Bug description:

During fuzzing of Python standard libraries, the following code snippet causes a TypeError with the following message: TypeError: '<' not supported between instances of 'NoneType' and 'int'. This occurs in the decode_params function at line 419 in email/utils.py.

import sys
import io
import email
d =  io.StringIO(open(sys.argv[1], "r").read())
email.message_from_file(d)

POC File:

https://github.com/FuturesLab/POC/blob/main/py-email/poc-02

Exception Trace

Traceback (most recent call last):
  File "rep.py", line 5, in <module>
    email.message_from_file(d)
  File "/usr/lib/python3.12/email/__init__.py", line 53, in message_from_file
    return Parser(*args, **kws).parse(fp)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/parser.py", line 54, in parse
    return feedparser.close()
           ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/feedparser.py", line 185, in close
    self._call_parse()
  File "/usr/lib/python3.12/email/feedparser.py", line 178, in _call_parse
    self._parse()
  File "/usr/lib/python3.12/email/feedparser.py", line 304, in _parsegen
    boundary = self._cur.get_boundary()
               ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/message.py", line 861, in get_boundary
    boundary = self.get_param('boundary', missing)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/message.py", line 725, in get_param
    for k, v in self._get_params_preserve(failobj, header):
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/message.py", line 674, in _get_params_preserve
    params = utils.decode_params(params)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/utils.py", line 419, in decode_params
    continuations.sort()
TypeError: '<' not supported between instances of 'NoneType' and 'int'

CPython versions tested on:

3.12, 3.11, 3.10, 3.9

Operating systems tested on:

Linux

[picnixz]

@bitdancer If possilbe, could you also have a look at:

• UnboundLocalError in email._header_value_parser.parse_message_id #134152
• AttributeError in email._header_value_parser.get_address #134155

TiA.

[bitdancer]

This issue is in the old code, not the new API. If someone feels like fixing it I'll review, but I'm not going to fix this one myself. I'll look at the other issues presently, which are in the new API.