CHARON: Polyglot Code Analysis for Detecting Vulnerabilities in Scripting Languages Native Extensions

Scripting languages like Python or JavaScript are extremely popular among developers, in part due to their massive open-source ecosystems that enable smooth code reuse. However, recent work shows that a lot of scripting code runs C/C++ code under the hood, via native extensions. This might introduce subtle security issues that can surprise the users. Prior work in this domain relies on simple, intra-procedural, flow-insensitive data flow analysis to detect such problems, but it is unclear if a more holistic polyglot static analysis could be feasible, and if so, what are its costs and benefits.In this work, we propose CHARON, the first inter-procedural, polyglot static analysis for detecting vulnerabilities in scripting languages. Our approach advocates for linking together the code property graphs of the different languages and performing cross-language data flow analysis by switching between code representations, when cross-language function calls are encountered. In this way, CHARON supports data flows that cross several times the language boundary, spanning multiple functions on either side. We evaluated CHARON on 11.8K polyglot packages from npm and PyPI, containing 896M lines of code. CHARON identified 5,813 manually-confirmed, vulnerable data flows in 116 packages. We performed a baseline comparison of CHARON with single-language analysis on native code, showing a ~6x increase in true positives and ~4%, less false positive alerts. We demonstrated exploitability of the discovered vulnerabilities by creating 63 PoCs across 34 packages, showing, among others, how we can escalate a buffer overflow vulnerability in native extensions to arbitrary code execution, which we believe to be the first of its kind. Overall, our results show that inter-procedural, polyglot analysis is both feasible and effective for detection of native extension vulnerabilities.