On the vulnerability proneness of multilingual code

Software construction using multiple languages has long been a norm, yet it is still unclear if multilingual code construction has significant security implications and real security consequences. This paper aims to address this question with a large-scale study of popular multi-language projects on GitHub and their evolution histories, enabled by our novel techniques for multilingual code characterization. We found statistically significant associations between the proneness of multilingual code to vulnerabilities (in general and of specific categories) and its language selection. We also found this association is correlated with that of the language interfacing mechanism, not that of individual languages. We validated our statistical findings with in-depth case studies on actual vulnerabilities, explained via the mechanism and language selection. Our results call for immediate actions to assess and defend against multilingual vulnerabilities, for which we provide practical recommendations.