CVE-2016-9136 in MuJS
Summary
by MITRE
Artifex Software, Inc. MuJS before a0ceaf5050faf419401fe1b83acfa950ec8a8a89 allows context-dependent attackers to obtain sensitive information by using the "crafted JavaScript" approach, related to a "Buffer Over-read" issue.
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Analysis
by VulDB Data Team • 05/26/2019
The vulnerability identified as CVE-2016-9136 represents a critical buffer over-read flaw within the MuJS JavaScript engine developed by Artifex Software. This issue manifests in versions of MuJS prior to commit a0ceaf5050faf419401fe1b83acfa950ec8a8a89, where the interpreter fails to properly validate input data during JavaScript execution. The vulnerability is classified as context-dependent, meaning its exploitation requires specific conditions and crafted input patterns that trigger the over-read behavior. Such vulnerabilities typically arise when the software reads memory locations beyond the bounds of allocated buffers, potentially exposing sensitive data from adjacent memory regions.
The technical implementation of this buffer over-read vulnerability occurs during JavaScript parsing and execution phases within the MuJS engine. When processing maliciously crafted JavaScript code, the engine's memory management routines fail to properly bounds-check array accesses or string operations, leading to unintended memory reads. This flaw falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions in software systems. The vulnerability is particularly concerning because it allows attackers to extract information from memory locations that should remain private, potentially including sensitive data such as cryptographic keys, passwords, or other confidential information stored in adjacent memory segments. The attack vector requires an attacker to have the ability to inject JavaScript code into an application that utilizes the vulnerable MuJS engine, making it a significant risk for web applications, embedded systems, or any software that incorporates JavaScript interpretation capabilities.
The operational impact of CVE-2016-9136 extends beyond simple information disclosure, as it can serve as a foundational vulnerability for more sophisticated attacks within the MITRE ATT&CK framework. This vulnerability can be leveraged as an information gathering primitive, enabling attackers to discover memory layout structures, heap organization patterns, or other sensitive data that could facilitate subsequent exploitation attempts. The vulnerability's presence in MuJS means that any application relying on this JavaScript engine for embedded scripting or dynamic content processing becomes susceptible to information leakage attacks. Organizations using affected versions of MuJS in their software products, web applications, or embedded systems face potential exposure of sensitive information through this over-read condition. The vulnerability's exploitation typically requires a combination of precise JavaScript crafting and specific runtime conditions, but once triggered, it can provide attackers with significant insights into the target system's memory state and potentially enable more advanced attack vectors such as heap spraying or information leakage for privilege escalation attempts.
Mitigation strategies for CVE-2016-9136 primarily focus on updating to patched versions of the MuJS engine where the buffer over-read conditions have been addressed through proper bounds checking and memory validation routines. Organizations should conduct comprehensive vulnerability assessments to identify all systems and applications that utilize the vulnerable MuJS versions, particularly those that process untrusted JavaScript input or execute dynamic code from external sources. The implementation of input validation controls, sandboxing mechanisms, and runtime protections can help reduce the attack surface, although these measures do not fully compensate for the underlying memory safety issues. Security teams should also consider implementing monitoring solutions that can detect anomalous memory access patterns or information disclosure attempts that may indicate exploitation of this vulnerability. Additionally, developers should adopt secure coding practices that emphasize bounds checking, memory safety validation, and proper input sanitization when working with JavaScript engines or similar interpreted environments. The vulnerability serves as a reminder of the critical importance of memory safety in interpreted languages and the necessity of regular security updates to address buffer over-read conditions that can expose sensitive system information.