Yeah these extensions are not present, are their any chances of running OS commands from database?What do you mean by "from database"? I think you need to lay down your requirement and goal more clearly.
Typically this means that given user only having psql, or some other backend protocol only, connect to the database are they able to execute arbitrary commands as the user running the PostgreSQL process on the host system.
Untrusted langauges are untrusted for specifically this reason. Without untrusted languages it requires privilege escalation to interact dynamically with the host operating system.
Assuming raised privileges it is presently impossible to prevent such dynamic interaction.
David J.
