mongo.c:315 in mongo_read_response

mongo_env_read_socket( conn, &head, sizeof( head ) );
mongo_env_read_socket( conn, &fields, sizeof( fields ) );

These socket read ops are not checked for an error, e.g., timeout.

The function ignores the error, will probably be out-of-sync, and will carry on with garbage. The read ops should be checked and appropriate action taken, probably closing the socket since message will be out-of-sync and the socket no longer useful.