Google's Project Zero has developed an exploit for a glibc vulnerability:
http://googleprojectzero.blogspot.de/2014/08/the-poisoned-nul-byte-2014-edition.html

Part of that exploit is abusing a memory leak in pkexec's parameter handling. While not in itself a security vulnerability, this memory leak makes exploiting other bugs easier.

This is the code in question in pkexec.c (starting line 543):
      else if (strcmp (argv[n], "--user") == 0 || strcmp (argv[n], "-u") == 0)
        {
          n++;
          if (n >= (guint) argc)
            {
              usage (argc, argv);
              goto out;
            }

          opt_user = g_strdup (argv[n]);
        }

If multiple -u arguments are set opt_user gets set multiple times, overwriting (and thus leaking) pointers of previous results.