CVE-2019-7396 in ImageMagick
Summary
by MITRE
In ImageMagick before 7.0.8-25, a memory leak exists in ReadSIXELImage in coders/sixel.c.
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Analysis
by VulDB Data Team • 07/06/2023
The vulnerability identified as CVE-2019-7396 represents a critical memory leak flaw within ImageMagick's SIXEL image processing functionality. This issue affects versions prior to 7.0.8-25 and specifically targets the ReadSIXELImage function located in the coders/sixel.c source file. The SIXEL format is a graphics format originally developed for terminal-based systems and is commonly used in legacy applications and certain specialized environments where raster graphics are displayed through terminal emulators. The memory leak occurs during the processing of SIXEL formatted images, which can be exploited by malicious actors to consume excessive system resources.
The technical implementation of this vulnerability stems from inadequate memory management within the SIXEL image reader component of ImageMagick. When processing malformed or specially crafted SIXEL images, the ReadSIXELImage function fails to properly release allocated memory blocks, leading to progressive memory consumption over time. This type of vulnerability falls under CWE-401, which specifically addresses improper management of dynamic memory allocation. The flaw manifests when the application processes SIXEL image data that contains certain malformed structures or excessive repetition patterns, causing the memory allocation routines to repeatedly allocate memory without corresponding deallocation operations.
The operational impact of this memory leak vulnerability extends beyond simple resource exhaustion, creating potential denial of service conditions that can severely impact system availability. An attacker capable of submitting malicious SIXEL images to an ImageMagick processing system could gradually consume all available memory on the target system, ultimately leading to system instability, application crashes, or complete system hangs. This vulnerability is particularly concerning in environments where ImageMagick is used as a backend service for image processing, such as web applications, content management systems, or automated image conversion services that accept user-uploaded files. The memory leak can be exploited through various attack vectors including web uploads, file processing pipelines, or any scenario where untrusted SIXEL image data is processed by the vulnerable software.
Mitigation strategies for CVE-2019-7396 primarily focus on immediate software updates to versions 7.0.8-25 or later, which contain the necessary patches to address the memory management issues in the SIXEL image reader. System administrators should also implement input validation measures to filter or reject suspicious SIXEL image files before processing, particularly in environments where user uploads are accepted. Additional protective measures include implementing resource limits and monitoring for abnormal memory usage patterns, which can help detect exploitation attempts. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers resource exhaustion attacks through memory leaks, and represents a classic example of how improper resource management in image processing libraries can create security risks. Organizations should also consider implementing sandboxing mechanisms or containerization for image processing tasks to limit the potential impact of such vulnerabilities. The fix implemented in the patched versions addresses the root cause by ensuring proper memory deallocation and implementing additional validation checks for SIXEL image structures, thereby preventing the accumulation of unreleased memory blocks during image processing operations.