According to Python Security Advisory PSF-2005-001,
The Python development team has discovered a flaw in the SimpleXMLRPCServer library module which can give remote attackers access to internals of the registered object or its module or possibly other modules. The flaw only affects Python XML-RPC servers that use the register_instance() method to register an object without a _dispatch() method. Servers using only register_function() are not affected. On vulnerable XML-RPC servers, a remote attacker may be able to view or modify globals of the module(s) containing the registered instance's class(es), potentially leading to data loss or arbitrary code execution. If the registered object is a module, the danger is particularly serious. For example, if the registered module imports the os module, an attacker could invoke the os.system() function.
Note: This vulnerability affects your system only if you're running SimpleXMLRPCServer-based server. This isn't harmful at all if you don't run any internet server written in Python or your server doesn't serve in XML-RPC protocol.