 The purpose of this study is to find the highest dose of mebendazole MBZ that can be safely given to people with malignant brain tumors in combination with the current standard of care temozolomide without causing severe side effects. We also want to find out if MBZ can slow the growth of the brain tumor. The study doctors have found that MBZ is effective against malignant brain tumors in the laboratory and animal models of brain tumors. 