CVE-2023-49552 in MJS
Summary
by MITRE • 01/03/2024
An Out of Bounds Write in Cesanta mjs 2.20.0 allows a remote attacker to cause a denial of service via the mjs_op_json_stringify function in the msj.c file.
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Analysis
by VulDB Data Team • 01/23/2024
The vulnerability identified as CVE-2023-49552 represents a critical out-of-bounds write condition within the Cesanta mjs JavaScript engine version 2.20.0. This flaw exists within the mjs_op_json_stringify function located in the msj.c source file, creating a potential pathway for remote attackers to execute denial of service attacks against affected systems. The mjs library is a lightweight JavaScript engine designed for embedded systems and IoT devices, making this vulnerability particularly concerning given the widespread deployment of such systems in critical infrastructure environments.
The technical nature of this vulnerability stems from improper bounds checking within the JSON stringification process. When the mjs_op_json_stringify function processes certain input data structures, it fails to validate array boundaries before writing data to memory locations. This allows an attacker to craft malicious input that causes the function to write beyond allocated memory buffers, potentially corrupting adjacent memory regions. The flaw manifests as an out-of-bounds write condition that can be triggered through carefully constructed JSON data passed to the affected JavaScript engine. According to CWE-787, this vulnerability maps directly to the Common Weakness Enumeration for out-of-bounds write vulnerabilities, which are classified as critical due to their potential for system instability and exploitation.
The operational impact of CVE-2023-49552 extends beyond simple denial of service, as the out-of-bounds write condition can lead to system crashes, memory corruption, and potentially more severe consequences depending on the target environment. In embedded systems and IoT devices that rely on mjs for scripting capabilities, this vulnerability could allow attackers to disrupt critical services or cause complete system failure. The remote attack vector means that adversaries can exploit this flaw without requiring physical access or local privileges, making it particularly dangerous in networked environments where such devices are exposed to external threats. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, as it enables remote exploitation of system resources through memory corruption.
Mitigation strategies for CVE-2023-49552 should prioritize immediate patching of affected systems to version 2.21.0 or later, which contains the necessary fixes for the out-of-bounds write condition. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing Cesanta mjs 2.20.0, particularly those deployed in critical infrastructure or IoT environments where the impact of denial of service could be severe. Network segmentation and access controls should be implemented to limit exposure of vulnerable systems to untrusted networks, while monitoring systems should be configured to detect anomalous JSON processing patterns that might indicate exploitation attempts. Additionally, developers should implement input validation and bounds checking in their own code when interacting with mjs functions to reduce the attack surface and provide defense-in-depth measures against similar vulnerabilities. The fix for this vulnerability demonstrates the importance of proper memory management and bounds checking in embedded JavaScript engines, particularly those deployed in resource-constrained environments where traditional security mitigations may not be available.