CVE-2020-36368 in MJS
Summary
by MITRE • 05/29/2021
Stack overflow vulnerability in parse_statement Cesanta MJS 1.20.1, allows remote attackers to cause a Denial of Service (DoS) via a crafted file.
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Analysis
by VulDB Data Team • 06/03/2021
The CVE-2020-36368 vulnerability represents a critical stack overflow flaw discovered in Cesanta MJS version 1.20.1, a lightweight JavaScript engine designed for embedded systems and IoT devices. This vulnerability specifically affects the parse_statement function within the MJS interpreter, creating a pathway for remote attackers to exploit the software through carefully crafted input files. The issue stems from inadequate input validation and memory management within the JavaScript parsing routine, where maliciously constructed JavaScript code can trigger excessive stack consumption during the parsing phase.
The technical implementation of this vulnerability involves the parse_statement function failing to properly bounds-check input data when processing JavaScript statements. When an attacker supplies a crafted file containing malformed or excessively nested JavaScript constructs, the function recursively processes these inputs without sufficient stack depth limitations. This leads to a stack overflow condition where the program's call stack exceeds its allocated memory space, resulting in an abrupt program termination and complete denial of service for the affected system. The vulnerability is particularly concerning because it can be triggered remotely through file upload mechanisms or network-based JavaScript execution contexts.
From an operational impact perspective, this vulnerability poses significant risks to embedded systems, IoT devices, and network appliances that utilize Cesanta MJS for scripting capabilities. The remote exploitation capability means attackers can compromise systems without requiring physical access or local privileges, making it particularly dangerous in networked environments. The DoS condition effectively renders the targeted device or application unusable until manual intervention occurs, potentially disrupting critical services in industrial control systems, smart home devices, or network infrastructure equipment. Organizations relying on MJS for embedded scripting may face widespread service disruption across their deployed devices.
Mitigation strategies for CVE-2020-36368 should prioritize immediate software updates to versions that address the stack overflow vulnerability through proper input validation and stack depth controls. System administrators must implement network segmentation and access controls to limit exposure to potentially malicious file uploads or remote JavaScript execution. The vulnerability aligns with CWE-121 Stack-based Buffer Overflow, indicating improper stack management during parsing operations, and may be categorized under ATT&CK technique T1203 Exploitation for Client Execution when targeting vulnerable embedded systems. Additional defensive measures include input sanitization at network boundaries, monitoring for unusual file upload patterns, and implementing runtime protections such as stack canaries or address space layout randomization to detect and prevent exploitation attempts. Organizations should conduct comprehensive vulnerability assessments of all systems utilizing Cesanta MJS to identify potential exposure and establish incident response procedures for handling such remote exploitation events.