Connect() hangs with SSH tunnels and 11g database

1. What versions are you using?
   Python 3.13.3 (also tried with 3.11)
   Oracledb 3.1.1 (also tried 3.0.0 and 2.5.1)
   Oracle database 11g
   Oracle instant client 18.5 (also tried with 12.2)

   platform.platform: Windows-11-10.0.26100-SP0
   sys.maxsize > 2**32: True
   platform.python_version: 3.13.3
   oracledb.version: 3.1.1

2. Is it an error or a hang or a crash? Hang

3. What error(s) or behavior you are seeing?
   While trying to connect to 11g databases through SSHtunnels, oracledb.connect() hangs and doesn't return anything.
   I tried it on multiple tunnels/databases combinaisons, while mixing oracledb / instantclient / python versions.

   If I open the tunnel through putty, oracledb.connect works.
   If I open the tunnel through another script, oracledb.connect works. (!)
   If I try to open a tunnel and connect to a 19c database, it works
   If I do the same thing using python 3.9 and cx_oracle, it works.

   If I provide a wrong username or password, I get an (expected) error.
   If I provide a wrong SID, I get an (expected) error.

   I do see an inactive connection in my v$session linked to my script.

   I tried everything I could think of and do not understand what I'm missing.

4. Does your application call init_oracle_client()? Yes, I tried with instant client versions 11.2, 12.1, 18.5
   I had success accessing a 19c db using instant client 21.18 through the same tunnel (and same script)

5. Include a runnable Python script that shows the problem.

from sshtunnel import SSHTunnelForwarder
import oracledb

# ssh config
ssh_host = "###_tunnel.com"
ssh_port = 21
ssh_username = "ssh_user"
ssh_password = "ssh_psw"

# db config
oracle_host = "ip.of.my.db"
oracle_port = 1521
oracle_sid = "DB_SID"
oracle_user = "DB_USER"
oracle_password = "DB_PSW"

#oracle_client_path = r"C:\instant_client18c\instantclient-basic-windows.x64-18.5.0.0.0dbru\instantclient_18_5"
oracle_client_path = r"C:\instant_client11g\instantclient-basic-windows.x64-11.2.0.4.0\instantclient_11_2"
oracledb.init_oracle_client(lib_dir=oracle_client_path)
print("Thin mode enabled?", oracledb.is_thin_mode())

try:
    with SSHTunnelForwarder(
            (ssh_host, ssh_port),
            ssh_username=ssh_username,
            ssh_password=ssh_password,
            remote_bind_address=(oracle_host, oracle_port),
    ) as tunnel:
        print(f"binding on {tunnel.local_bind_host}:{tunnel.local_bind_port}")
        print(oracledb.clientversion())
        param = oracledb.ConnectParams(
            user=oracle_user,
            password=oracle_password,
            host="localhost",
            port=tunnel.local_bind_port,
            sid=oracle_sid,
        )
        with oracledb.connect(params=param) as connection:
            print("connected to Oracle 11.2!") # this never prints for tunnel + 11g
            with connection.cursor() as cursor:
                cursor.execute("SELECT 'query success' AS TEST FROM dual")
                result = cursor.fetchone()
                print(result[0])

except Exception as e:
    print(f"Error : {e}")

Start with the provided Python reproduction using SSHTunnelForwarder, oracledb.connect(), and Oracle 11g, then compare it with the working 19c and external-tunnel cases. Check the reported client, Python, SID, and credential combinations. Done means identifying and addressing the cause of the hang while preserving successful connections and expected errors.