CVE-2019-16366 in XS
Summary
by MITRE
In XS 9.0.0 in Moddable SDK OS180329, there is a heap-based buffer overflow in fxBeginHost in xsAPI.c when called from fxRunDefine in xsRun.c, as demonstrated by crafted JavaScript code to xst.
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Analysis
by VulDB Data Team • 12/25/2023
The vulnerability CVE-2019-16366 represents a critical heap-based buffer overflow within the Moddable SDK's XS JavaScript engine version 9.0.0, specifically affecting the OS180329 release. This flaw exists in the xsAPI.c file at the fxBeginHost function, which is invoked from fxRunDefine in xsRun.c, creating a chain of execution that can be exploited through carefully crafted JavaScript code sent to the xst interpreter. The issue demonstrates a classic memory safety vulnerability that can lead to arbitrary code execution and system compromise.
The technical flaw stems from inadequate bounds checking within the XS JavaScript engine's host initialization process. When fxBeginHost processes incoming JavaScript code through the xst interpreter, it fails to properly validate the size of memory allocations required for processing the input data. This oversight allows an attacker to craft malicious JavaScript payloads that deliberately exceed buffer boundaries during memory allocation, causing the heap to overflow. The vulnerability specifically manifests when the engine attempts to define and execute host-level JavaScript constructs, making it particularly dangerous in environments where untrusted code execution is possible.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides attackers with potential pathways for privilege escalation and system compromise. The heap overflow can be leveraged to overwrite critical memory structures, potentially leading to arbitrary code execution with the privileges of the running process. This makes the vulnerability particularly dangerous in embedded systems, IoT devices, and mobile applications that utilize the Moddable SDK, where the JavaScript engine serves as a core component for application logic execution. The vulnerability affects the broader ecosystem of devices and applications built using the Moddable SDK, creating widespread potential for exploitation across multiple deployment scenarios.
Mitigation strategies for CVE-2019-16366 should focus on immediate patching of the Moddable SDK to version 9.0.1 or later, which contains the necessary bounds checking fixes for the heap overflow condition. Organizations should implement strict input validation for all JavaScript code executed within the XS engine, particularly when processing untrusted inputs from external sources. Additionally, deployment environments should utilize address space layout randomization and stack canaries to make exploitation more difficult, while implementing proper memory access controls and monitoring for anomalous heap behavior. This vulnerability aligns with CWE-121 heap-based buffer overflow patterns and could be mapped to ATT&CK techniques involving code injection and privilege escalation through memory corruption exploits.