CVE-2016-9108 in MuJS
Summary
by MITRE
Integer overflow in the js_regcomp function in regexp.c in Artifex Software, Inc. MuJS before commit b6de34ac6d8bb7dd5461c57940acfbd3ee7fd93e allows attackers to cause a denial of service (application crash) via a crafted regular expression.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-9108 represents a critical integer overflow flaw within the MuJS JavaScript interpreter developed by Artifex Software. This issue specifically affects versions of MuJS prior to commit b6de34ac6d8bb7dd5461c57940acfbd3ee7fd93e, making it a significant concern for systems that rely on this embedded JavaScript engine for scripting functionality. The vulnerability resides in the js_regcomp function located within the regexp.c source file, which is responsible for compiling regular expressions for pattern matching operations. This integer overflow condition occurs during the processing of crafted regular expressions that manipulate the internal integer variables used for memory allocation calculations.
The technical exploitation of this vulnerability leverages the inherent flaw in how MuJS handles regular expression compilation, particularly when processing malformed input patterns. When an attacker submits a specially crafted regular expression, the js_regcomp function performs integer arithmetic operations that exceed the maximum representable value for the integer data type, resulting in an integer overflow condition. This overflow corrupts the program's memory state and leads to unpredictable behavior including application crashes, memory corruption, and potential system instability. The vulnerability specifically targets the integer overflow scenario classified under CWE-190, which deals with integer overflow leading to buffer overflows and memory corruption issues.
From an operational perspective, this vulnerability presents a severe denial of service risk that can be easily exploited by remote attackers without requiring authentication or specialized privileges. The impact extends beyond simple service disruption as the application crash can potentially lead to more serious consequences including data loss or system instability in environments where MuJS is embedded within larger applications. Systems utilizing MuJS for scripting capabilities, particularly those exposed to untrusted input such as web applications, content management systems, or embedded devices, face significant risk from this vulnerability. The ATT&CK framework categorizes this type of vulnerability under the T1499.004 technique for "Network Denial of Service" as it enables attackers to disrupt services through controlled resource exhaustion or application instability.
Mitigation strategies for CVE-2016-9108 should prioritize immediate patching of affected MuJS versions to the fixed commit referenced in the vulnerability description. Organizations should implement input validation and sanitization measures for all regular expression inputs to prevent exploitation attempts, while also considering the implementation of regular expression timeouts or execution limits to prevent resource exhaustion attacks. Network segmentation and access controls should be enforced to limit exposure of systems running vulnerable versions of MuJS, particularly in internet-facing environments. Additionally, monitoring systems should be configured to detect unusual patterns of regular expression processing that might indicate attempted exploitation, and regular security audits should verify that all embedded JavaScript interpreters within the organization's infrastructure are updated to secure versions. The vulnerability demonstrates the critical importance of proper integer handling and bounds checking in security-sensitive applications, particularly those that process untrusted input data through complex parsing operations.