CVE-2021-46554 in MJS
Summary
by MITRE • 01/28/2022
Cesanta MJS v2.20.0 was discovered to contain a SEGV vulnerability via mjs_json_stringify at src/mjs_json.c. This vulnerability can lead to a Denial of Service (DoS).
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Analysis
by VulDB Data Team • 01/30/2022
The vulnerability identified as CVE-2021-46554 affects Cesanta MJS version 2.20.0, a lightweight JavaScript engine designed for embedded systems and IoT devices. This security flaw manifests as a segmentation fault (SEGV) within the mjs_json_stringify function located in the src/mjs_json.c source file, representing a critical weakness in the JSON processing capabilities of this embedded JavaScript interpreter. The issue stems from inadequate input validation and memory management within the JSON stringification routine, which fails to properly handle malformed or unexpected input data structures.
The technical implementation of this vulnerability occurs when the mjs_json_stringify function processes certain input parameters that trigger memory access violations or improper pointer dereferences. This function is responsible for converting JavaScript objects and values into JSON string representations, making it a critical component in applications that rely on JSON serialization for data exchange. When malformed input reaches this function, the lack of proper boundary checking and validation causes the JavaScript engine to attempt accessing invalid memory addresses, resulting in a segmentation fault that terminates the application process.
The operational impact of this vulnerability extends beyond simple application crashes, as it creates a reliable Denial of Service condition that can be exploited by malicious actors or through accidental input corruption. In embedded systems and IoT environments where Cesanta MJS is commonly deployed, such a vulnerability could lead to complete service disruption, potentially affecting critical infrastructure components, industrial control systems, or consumer devices that depend on stable JavaScript execution environments. The vulnerability's exploitability is particularly concerning given that JSON processing is a fundamental operation in web applications, REST APIs, and data communication protocols that these systems typically employ.
Organizations utilizing Cesanta MJS v2.20.0 should implement immediate mitigations including upgrading to a patched version of the software, implementing input sanitization measures before JSON processing, and deploying runtime monitoring to detect potential exploitation attempts. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and may also relate to CWE-476, pointer issues, as the segmentation fault indicates improper memory handling. From an ATT&CK perspective, this vulnerability could be leveraged as part of a broader attack chain under the T1499.004 technique for network denial of service, potentially enabling adversaries to disrupt services in IoT and embedded systems environments where such JavaScript engines are prevalent. Additionally, the vulnerability demonstrates characteristics consistent with T1595.001, targeting the network infrastructure through application-level flaws that can be exploited to compromise system availability and reliability.