I am facing this error while using Cx_Oracle package in python environment. I upgraded to oracle 12c from 11g but it still gets me this error. Also, I am using ojdbc6.jar.
DatabaseError: ORA-28040: No matching authentication protocol
ojdbc6.jar is driver for JVM/Java
Cx_Oracle is C/C++ library depending on libclnth.so library.
The errors states that your client is either to old (or too new) and you can not authenticate to the database. There is no auth protocol that both sides implement/accept.
Either you should upgrade your client or change
sqlnet.ora set SQLNET.ALLOWED_LOGON_VERSION to version of your client library.
Cx_Oracle : DatabaseError: ORA-28040: No matching authentication protocol