hang in connection.cpp at static SqlHandlePtr getEnvHandle()

[ywy0003]

Describe the bug

Consistent hang attempting to connect to database when run on Debian Linux. This same code works as expected on Windows.

I confirmed network connectivity with the following.

nc -z SQL-PD01.domain-redacted 1433
SQL-PD01.domain-redacted [10.156.65.100] 1433 (ms-sql-s) open

Below is a log listing with debug enabled for the mssql-python module.

2026-02-04 11:36:52.132, 26358, DEBUG, logging.py:368, Python, PoolingManager.disable: Attempting to disable pooling
2026-02-04 11:36:52.132, 26358, DEBUG, logging.py:368, Python, PoolingManager.disable: Pooling already disabled or closed
2026-02-04 11:36:52.132, 26358, DEBUG, logging.py:368, Python, sanitize_connection_string: Sanitizing connection string (length=196)
2026-02-04 11:36:52.133, 26358, DEBUG, logging.py:368, Python, sanitize_connection_string: Password fields masked
2026-02-04 11:36:52.133, 26358, INFO, logging.py:368, Python, Final connection string: Driver={ODBC Driver 18 for SQL Server};APP=MSSQL-Python;Database=BusinessViews;PWD=***;Server=tcp:SQL-PD01.domain-redacted,1433;UID=studentrecords_reader
2026-02-04 11:36:52.133, 26358, DEBUG, connection.cpp:22, DDBC, Allocating ODBC environment handle
2026-02-04 11:36:52.133, 26358, DEBUG, connection.cpp:24, DDBC, Function pointers not initialized, loading driver
*** hang occurs. no further log messages ***

To reproduce

Include a complete code listing (or project/solution) that we can run to reproduce the issue.

import logging
import mssql_python

from sys import argv, stdout

hostname = argv[1]
database = argv[2]
username = argv[3]
password = argv[4]

root = logging.getLogger()
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler(stdout)
handler.setLevel(logging.DEBUG)
root.addHandler(handler)

mssql_python.setup_logging(output="stdout")
mssql_python.pooling(enabled=False)

connection_string = f"SERVER=tcp:{hostname},1433;DATABASE={database};UID={username};PWD={password};"
conn = mssql_python.connect(connection_string)  # hangs here

cur = conn.cursor()
result = cur.execute("SELECT @@VERSION")
for row in result:
    print(row)
cur.close()
conn.close()```


### Expected behavior
Expected a successful connection to the database, or an exception. The following is what I see when running this code on Windows.

2026-02-04 11:31:51.050, 25812, DEBUG, connection.cpp:22, DDBC, Allocating ODBC environment handle
2026-02-04 11:31:51.062, 25812, DEBUG, connection.cpp:61, DDBC, Allocating SQL Connection Handle
2026-02-04 11:31:51.062, 25812, DEBUG, connection.cpp:68, DDBC, Connecting to database
2026-02-04 11:31:51.167, 25812, DEBUG, connection.cpp:182, DDBC, Setting autocommit=0
2026-02-04 11:31:51.175, 25812, DEBUG, connection.cpp:190, DDBC, Autocommit disabled
2026-02-04 11:31:51.175, 25812, DEBUG, logging.py:368, Python, cursor: Creating new cursor - timeout=0, total_cursors=0
2026-02-04 11:31:51.175, 25812, DEBUG, connection.cpp:213, DDBC, Allocating statement handle
2026-02-04 11:31:51.175, 25812, DEBUG, logging.py:368, Python, cursor: Cursor created successfully - total_cursors=1

### Further technical details
Python version: CPython 3.14.2
SQL Server version: Microsoft SQL Server 2019 (RTM-CU32-GDR) (KB5065222) - 15.0.4445.1 (X64)
Operating system: Windows Server 2019 Datacenter 10.0 <X64> (Build 17763: ) (Hypervisor)


**Additional context**
N/A

[gordthompson]

I am unable to reproduce your issue with Debian 13.3.

~/mydockerbuild/my_app.py

import logging
import mssql_python

from sys import argv, stdout

hostname = argv[1]
database = argv[2]
username = argv[3]
password = argv[4]

root = logging.getLogger()
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler(stdout)
handler.setLevel(logging.DEBUG)
root.addHandler(handler)

mssql_python.setup_logging(output="stdout")
mssql_python.pooling(enabled=False)

connection_string = (
    f"SERVER=tcp:{hostname},1433;DATABASE={database};UID={username};PWD={password};"
    "TrustServerCertificate=yes;"
)
conn = mssql_python.connect(connection_string)  # hangs here -- not for me

cur = conn.cursor()
result = cur.execute("SELECT @@VERSION")
for row in result:
    print(row)
cur.close()
conn.close()

~/mydockerbuild/my_dockerfile

FROM debian:13.3
WORKDIR /app
COPY my_app.py my_app.py
RUN apt-get update 
RUN apt-get install -y python3-venv
RUN apt-get install -y libltdl7 libkrb5-3 libgssapi-krb5-2 krb5-user
RUN python3 -m venv venv
RUN venv/bin/pip install mssql-python
RUN venv/bin/python my_app.py 192.168.0.199 test scott tiger^5HHH

When I do

docker build --no-cache --progress=plain  ~/mydockerbuild -f my_dockerfile -t issue_421

it runs to completion without hanging.

[ywy0003]

Gord, I appreciate that data point and expected such. Unfortunately, I am unable to update the computer, which is managed by a different team. I did submit such a request, but upgrading that system seems at least months away. I would like to understand why the Microsoft code hangs on Debian 10. I expect the code to fail with an error when unable to function as expected.

[ywy0003]

Ahh, I see now. I wrote at the top of my issue that the code hangs on Debian Linux, but did not specify the version. Near the bottom, I listed the operating system of the SQL server, not the OS running the Python code. That's my mistake. The Python code is running on Debian 10 "buster". Sorry for the confusion.