During fuzzing of Python standard libraries, the following code snippet causes an UnboundLocalError with the following message: UnboundLocalError: cannot access local variable 'pos' where it is not associated with a value'. This occurs in the _get_ptext_to_endchars function at line 1035 in email/_header_value_parser.py.

import email._header_value_parser
email._header_value_parser.parse_message_id("<T@[")

Exception Trace

Traceback (most recent call last):
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2118, in get_msg_id
    token, value = get_dot_atom_text(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1344, in get_dot_atom_text
    raise errors.HeaderParseError("expected atom at a start of "
email.errors.HeaderParseError: expected atom at a start of dot-atom-text but found '['
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "rep.py", line 2, in <module>
    email._header_value_parser.parse_message_id("<T@[")
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2149, in parse_message_id
    token, value = get_msg_id(value)
                   ^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2121, in get_msg_id
    token, value = get_no_fold_literal(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2066, in get_no_fold_literal
    token, value = get_dtext(value)
                   ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1557, in get_dtext
    ptext, value, had_qp = _get_ptext_to_endchars(value, '[]')
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1033, in _get_ptext_to_endchars
    pos = pos + 1
          ^^^
UnboundLocalError: cannot access local variable 'pos' where it is not associated with a value

Exception Trace

CPython versions tested on:

Operating systems tested on:

Linked PRs