CVE-2016-5239 in ImageMagick
Summary
by MITRE
The gnuplot delegate functionality in ImageMagick before 6.9.4-0 and GraphicsMagick allows remote attackers to execute arbitrary commands via unspecified vectors.
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Analysis
by VulDB Data Team • 03/16/2017
The vulnerability identified as CVE-2016-5239 represents a critical command execution flaw within the ImageMagick image processing library and its GraphicsMagick counterpart. This issue affects versions prior to 6.9.4-0 and stems from the gnuplot delegate functionality that enables these libraries to process gnuplot data files. The vulnerability allows remote attackers to execute arbitrary commands on systems running affected versions of ImageMagick or GraphicsMagick, creating a significant security risk for web applications and services that process user-uploaded images. The flaw specifically resides in how these libraries handle gnuplot delegate operations, where insufficient input validation permits maliciously crafted data to trigger unintended command execution sequences.
The technical implementation of this vulnerability involves the improper handling of gnuplot data files within the image processing pipeline. When ImageMagick or GraphicsMagick encounters a file that utilizes gnuplot delegate functionality, the system fails to properly sanitize user-supplied input before passing it to underlying command execution mechanisms. This allows attackers to inject malicious commands that get executed with the privileges of the process running the image processing library. The vulnerability operates at the intersection of image processing and command execution, where the library's delegate system is designed to handle external tools but lacks proper input sanitization controls. This flaw aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, making it a classic command injection vulnerability.
The operational impact of CVE-2016-5239 is severe and far-reaching across various computing environments. Web applications that utilize ImageMagick or GraphicsMagick for image processing are particularly vulnerable, as attackers can exploit this flaw through file upload mechanisms to execute arbitrary commands on the server. This vulnerability enables attackers to perform actions such as reading system files, executing shell commands, establishing reverse shells, or even gaining full system compromise. The remote nature of the attack means that exploitation can occur without requiring local system access, making it particularly dangerous for publicly accessible web services. The vulnerability affects not only web applications but also any system that processes images through these libraries, including content management systems, file upload services, and automated image processing workflows.
Organizations should implement immediate mitigations to address this vulnerability by upgrading to ImageMagick version 6.9.4-0 or later and GraphicsMagick versions that include the relevant fixes. The upgrade process should be prioritized across all systems that utilize these libraries for image processing, with particular attention to web-facing applications and services. Additional protective measures include implementing strict file type validation, disabling gnuplot delegate functionality if not required, and configuring proper input sanitization for all image processing operations. Network segmentation and access controls should be enforced to limit potential attack surfaces, while monitoring systems should be deployed to detect suspicious file processing activities. Security teams should also consider implementing application firewalls and web application security controls to prevent exploitation attempts. The vulnerability demonstrates the importance of proper input validation and privilege separation in image processing libraries, aligning with ATT&CK technique T1059.001 for command and scripting interpreter execution. Organizations should also review their overall security posture and implement comprehensive vulnerability management processes to identify and remediate similar issues in other third-party libraries and software components.