CVE-2018-16749 in ImageMagick
Summary
by MITRE
In ImageMagick 7.0.7-29 and earlier, a missing NULL check in ReadOneJNGImage in coders/png.c allows an attacker to cause a denial of service (WriteBlob assertion failure and application exit) via a crafted file.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16749 represents a critical denial of service flaw within ImageMagick's handling of JNG (JPEG Network Graphics) image files. This issue affects versions 7.0.7-29 and earlier, where the software fails to properly validate input data during the image reading process. The flaw specifically manifests in the ReadOneJNGImage function located within the coders/png.c source file, which is responsible for processing JNG format images. When an attacker crafts a malicious JNG file, the application encounters a scenario where a crucial NULL pointer check is omitted, leading to a cascade of failures that ultimately results in application termination.
The technical implementation of this vulnerability stems from a fundamental lack of input validation within the image processing pipeline. During the parsing of JNG files, the ReadOneJNGImage function does not adequately verify that certain pointers remain valid before attempting to access them. This missing NULL check creates a condition where the WriteBlob assertion failure occurs, which is a critical internal consistency check that ImageMagick performs to ensure proper data handling. When this assertion fails due to the malformed input, the application cannot continue its normal execution flow and terminates abruptly. The vulnerability is particularly concerning because it can be triggered through simple file manipulation without requiring any special privileges or complex attack vectors, making it easily exploitable by malicious actors who wish to disrupt services.
From an operational perspective, this vulnerability poses significant risks to systems that process user-uploaded images or handle image processing workflows. The denial of service impact means that applications relying on ImageMagick for image conversion, manipulation, or display can be rendered completely non-functional by a single malicious file. This affects web applications, content management systems, and any platform that accepts image uploads from untrusted sources. The vulnerability can be exploited in various contexts including web applications, automated image processing pipelines, and content delivery networks where ImageMagick is used as a backend image processing tool. The ease of exploitation, combined with the potential for widespread service disruption, makes this a particularly dangerous flaw in environments where continuous availability is critical.
The underlying cause of this vulnerability aligns with CWE-476, which describes NULL Pointer Dereference, a common class of software flaws that occur when programs attempt to access memory through a pointer that has not been properly initialized or validated. From an attack perspective, this vulnerability maps to several ATT&CK techniques including T1499.004 for Network Denial of Service and T1059.007 for Command and Scripting Interpreter. The flaw demonstrates how seemingly benign file format processing can become a vector for system disruption, highlighting the importance of robust input validation in multimedia processing libraries. Organizations should implement immediate mitigations including updating to ImageMagick version 7.0.7-30 or later, which contains the necessary NULL pointer checks to prevent the assertion failure. Additionally, implementing proper input sanitization, file type validation, and restricting image processing capabilities for untrusted inputs can help reduce the attack surface. System administrators should also consider implementing monitoring and alerting for unusual application termination events that could indicate exploitation attempts.