CVE-2016-9294 in MuJS
Summary
by MITRE
Artifex Software, Inc. MuJS before 5008105780c0b0182ea6eda83ad5598f225be3ee allows context-dependent attackers to conduct "denial of service (application crash)" attacks by using the "malformed labeled break/continue in JavaScript" approach, related to a "NULL pointer dereference" issue affecting the jscompile.c component.
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Analysis
by VulDB Data Team • 10/03/2022
The vulnerability identified as CVE-2016-9294 represents a critical denial of service flaw within the MuJS JavaScript engine developed by Artifex Software. This issue manifests when the engine processes malformed JavaScript code containing labeled break or continue statements that trigger a NULL pointer dereference condition. The vulnerability exists in MuJS versions prior to commit 5008105780c0b0182ea6eda83ad5598f225be3ee, making affected systems susceptible to application crashes that can disrupt normal operations. The flaw specifically impacts the jscompile.c component, which handles JavaScript compilation processes within the engine.
The technical exploitation of this vulnerability occurs through carefully crafted JavaScript code that contains malformed labeled break or continue statements. When the MuJS engine attempts to process such malformed constructs, it encounters a NULL pointer dereference during the compilation phase, leading to an application crash. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions that can result in system instability and denial of service. The context-dependent nature of this flaw means that exploitation requires specific JavaScript code patterns that trigger the compilation error, making it more difficult to exploit automatically but still potentially dangerous in environments where untrusted JavaScript code is executed.
The operational impact of this vulnerability extends beyond simple application crashes to potentially compromise system availability and service integrity. Organizations that utilize MuJS for embedded JavaScript processing, web application frameworks, or document processing systems may experience unexpected service interruptions when malicious or malformed JavaScript code is processed. The vulnerability is particularly concerning in environments where JavaScript execution is not properly sandboxed or validated, as it can be exploited by attackers to disrupt services or perform denial of service attacks against applications that depend on the MuJS engine. This vulnerability directly aligns with ATT&CK technique T1499 which covers network denial of service attacks and can be leveraged in broader attack chains targeting system availability.
Mitigation strategies for CVE-2016-9294 should focus on immediate patching of affected MuJS versions to the fixed commit referenced in the vulnerability description. Organizations should also implement input validation and sanitization measures to prevent untrusted JavaScript code from reaching the MuJS engine. Additional protective measures include deploying application firewalls, implementing strict JavaScript code execution policies, and ensuring proper sandboxing of JavaScript processing environments. Security monitoring should be enhanced to detect unusual application crash patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of thorough input validation and error handling in scripting engines, particularly those used in embedded systems or applications processing untrusted code. Regular security assessments and updates of JavaScript engine components remain essential practices for maintaining system security posture against similar vulnerabilities.