BUG: DataFrame.fillna() with ArrowDtype(pa.null()) columns causes Arrow C++ assertion failure (core dump)

[aa89113]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
import pyarrow as pa

null_col = pd.array([pd.NA], dtype=pd.ArrowDtype(pa.null()))
df = pd.DataFrame({"x": null_col})
df_orig  = pd.DataFrame({"x": null_col})
df.fillna(df_orig)  # → core dump / Arrow C++ assertion

Issue Description

BUG: DataFrame.fillna() with ArrowDtype(pa.null()) columns causes Arrow C++ assertion failure (core dump)

Expected Behavior

No core dump

Installed Versions

INSTALLED VERSIONS

commit : 9c8bc3e
python : 3.11.8
python-bits : 64
OS : Linux
OS-release : 4.18.0-553.16.1.el8_10.x86_64
Version : #1 SMP Thu Aug 1 04:16:12 EDT 2024
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.3.3
numpy : 1.26.4
pytz : 2026.1.post1
dateutil : 2.9.0.post0
pip : 26.1.1
Cython : 3.2.4
sphinx : None
IPython : 9.10.1
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.14.3
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : 2026.3.0
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : 6.0.4
matplotlib : 3.10.0
numba : 0.62.1
numexpr : None
odfpy : None
openpyxl : 3.1.5
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : 23.0.1
pyreadstat : None
pytest : 9.0.3
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.16.3
sqlalchemy : None
tables : None
tabulate : 0.10.0
xarray : 2026.4.0
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2026.1
qtpy : None
pyqt5 : None

[jorisvandenbossche]

This is a upstream pyarrow bug, see apache/arrow#47447

[sarthaksaitwal]

Can i work on this issue?