CVE-2019-9956 in ImageMagick
Summary
by MITRE
In ImageMagick 7.0.8-35 Q16, there is a stack-based buffer overflow in the function PopHexPixel of coders/ps.c, which allows an attacker to cause a denial of service or code execution via a crafted image file.
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Analysis
by VulDB Data Team • 08/04/2023
The vulnerability identified as CVE-2019-9956 represents a critical stack-based buffer overflow flaw within ImageMagick's image processing library, specifically affecting version 7.0.8-35 Q16. This vulnerability resides in the PopHexPixel function located within the coders/ps.c file, which handles the parsing of PostScript image data. The flaw arises when ImageMagick processes specially crafted image files that contain malformed hexadecimal pixel data, creating conditions where memory operations exceed allocated stack buffer boundaries. Such buffer overflows are particularly dangerous because they can be exploited to execute arbitrary code or cause system crashes through controlled memory corruption.
The technical exploitation of this vulnerability occurs during the parsing of PostScript files where the PopHexPixel function fails to properly validate input data length before writing to stack-allocated buffers. When an attacker crafts a malicious image file containing excessive hexadecimal pixel data, the function attempts to write beyond the predetermined buffer limits, potentially overwriting adjacent stack memory including return addresses and function parameters. This type of vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which is classified as a high-severity weakness in the Common Weakness Enumeration catalog. The attack vector is particularly concerning because it requires no special privileges beyond the ability to process image files, making it exploitable through various attack surfaces including web applications, email attachments, and file sharing systems.
The operational impact of CVE-2019-9956 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities that could allow attackers to compromise systems running vulnerable versions of ImageMagick. When exploited successfully, this vulnerability could enable attackers to execute malicious code with the privileges of the ImageMagick process, potentially leading to full system compromise. The vulnerability affects any system that processes PostScript image formats through ImageMagick, including web servers, content management systems, and image processing applications that utilize this library. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1203 for Exploitation for Client Execution, as it allows for arbitrary code execution through file processing. The vulnerability is particularly dangerous in environments where users can upload or process untrusted image files, as it provides a direct path for remote attackers to gain system access through image file manipulation.
Mitigation strategies for CVE-2019-9956 should focus on immediate version updates to ImageMagick 7.0.8-36 or later, which contain patches addressing the buffer overflow in the PopHexPixel function. Organizations should implement strict input validation and sanitization for all image file processing, particularly when handling untrusted content from external sources. Network segmentation and privilege separation can help limit the impact of successful exploitation by reducing the attack surface and preventing lateral movement. Additionally, implementing application whitelisting and restricting the execution of image processing utilities to trusted users can provide defense-in-depth measures. Security monitoring should include detection of unusual image processing activities and potential exploitation attempts through file upload mechanisms. The vulnerability serves as a reminder of the importance of regular security patching and the need for comprehensive input validation in multimedia processing libraries that handle untrusted data from diverse sources.