Interpreter Memory Safety via Differential Fuzzing with a CHERI on Top

Abstract

Memory safety is a critical issue in embedded systems. Although high-level languages like MicroPython simplify IoT development, their C-based runtimes remain vulnerable to memory errors triggered by Python code or native extensions. The CHERI (Capability Hardware Enhanced RISC Instructions) architecture offers hardware-enforced memory safety, but its effectiveness for exposing latent bugs in real-world interpreters has not yet been fully explored. We present diffCHERI:FruitFly, a novel differential testing framework for systematically uncovering memory defects in MicroPython across conventional (x86/ARM) and CHERI-enabled (Arm Morello) platforms. We mine historic vulnerabilities from diverse Python runtimes to extract recurring stress patterns, then use a large language model to generate new test programs, and apply Concrete Syntax Tree (CST) mutation to diversify inputs.