BUG: Cope with unbalanced delimiters in dictionary object (#2878)

Closes #2877.

pypdf/generic/_data_structures.py

@@ -570,6 +570,8 @@ def read_unsized_from_stream(
             try:
                 try:
                     key = read_object(stream, pdf)
+                    if isinstance(key, NullObject):
+                        break
                     if not isinstance(key, NameObject):
                         raise PdfReadError(
                             f"Expecting a NameObject for key but found {key!r}"

tests/test_reader.py

@@ -1703,3 +1703,12 @@ def test_space_in_names_to_continue_processing(caplog):
     reader = PdfReader(BytesIO(b), strict=True)
     with pytest.raises(PdfReadError):
         obj = reader.get_object(70)
+
+
+@pytest.mark.enable_socket()
+def test_unbalanced_brackets_in_dictionary_object(caplog):
+    """Cf #2877"""
+    url = "https://github.com/user-attachments/files/17162634/7f40cb209fb97d1782bffcefc5e7be40.pdf"
+    name = "iss2877.pdf"  # reused
+    reader = PdfReader(BytesIO(get_data_from_url(url, name=name)))
+    assert len(reader.pages) == 43  # note:  /Count = 46 but 3 kids are None