CVE-2017-5628 in MuJS
Summary
by MITRE
An issue was discovered in Artifex Software, Inc. MuJS before 8f62ea10a0af68e56d5c00720523ebcba13c2e6a. The MakeDay function in jsdate.c does not validate the month, leading to an integer overflow when parsing a specially crafted JS file.
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Analysis
by VulDB Data Team • 05/17/2026
The vulnerability identified as CVE-2017-5628 resides within the MuJS JavaScript engine developed by Artifex Software, Inc., specifically affecting versions prior to the commit hash 8f62ea10a0af68e56d5c00720523ebcba13c2e6a. This flaw manifests in the jsdate.c source file where the MakeDay function fails to properly validate month parameters during JavaScript date parsing operations. The absence of input validation creates a critical security gap that allows malicious actors to craft specially formatted JavaScript files designed to exploit this weakness. The vulnerability represents a classic example of insufficient input validation, which falls under the CWE-20 category of "Improper Input Validation" and can be classified as a buffer overflow condition when the integer overflow occurs during date calculation operations.
The technical exploitation of this vulnerability occurs when the MakeDay function processes month values that exceed normal boundaries, causing arithmetic operations to wrap around and produce unexpected integer values. This integer overflow condition can lead to memory corruption within the JavaScript engine's internal date handling mechanisms, potentially allowing attackers to manipulate memory layout and execute arbitrary code. The flaw is particularly dangerous because it operates at the parsing level of JavaScript execution, meaning that any web application or system utilizing MuJS for JavaScript processing could be compromised simply by loading a malicious script. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript' where an attacker could leverage this flaw to execute malicious JavaScript code with elevated privileges.
The operational impact of CVE-2017-5628 extends beyond simple denial of service conditions to potentially enable remote code execution within applications that depend on MuJS for JavaScript processing. Systems using vulnerable versions of MuJS could be at risk when processing untrusted JavaScript content, including web browsers, server-side JavaScript applications, or any software that embeds the MuJS engine for scripting capabilities. The integer overflow could result in unpredictable behavior, memory corruption, or complete system compromise depending on the execution context and how the vulnerable engine is integrated into larger applications. Organizations utilizing Artifex Software's MuJS in production environments should consider this vulnerability as a critical security concern requiring immediate remediation. The vulnerability's exploitation potential aligns with ATT&CK technique T1203 'Exploitation for Client Execution' and T1068 'Exploitation for Privilege Escalation', making it particularly dangerous in environments where the engine is used for processing potentially malicious user input or in web applications that execute third-party JavaScript code. Mitigation strategies should include immediate upgrading to the patched version of MuJS, implementing input validation controls, and monitoring for suspicious JavaScript execution patterns that might indicate exploitation attempts.