It was reported [1] that a flaw exists in graphite-web versions 0.9.5 through to 0.9.10, due to the use of the pickle module.  The clustering feature of graphite-web was introduced in 0.9.5 to facilitate scaling for a graphite setup, which was achieved by passing pickled data between servers.  However, upon receipt of the pickled data, no validation was done to limit the types of objects that are unpickled, which creates a condition where arbitrary code can be executed.  Based on the available metasploit module [2], it does not look as though any kind of authentication or validation between servers exists either, to prevent a remote unauthenticated user from exploiting this flaw.

This flaw has been fixed in 0.9.11 (git commit [3]).

[1] http://ceriksen.com/2013/08/20/graphite-remote-code-execution-vulnerability-advisory/
[2] https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/webapp/graphite_pickle_exec.rb
[3] https://github.com/graphite-project/graphite-web/commit/c198e5836970f0970b96498fcbe6fa83d90110cf