CVE-2016-9556 in ImageMagick
Summary
by MITRE
The IsPixelGray function in MagickCore/pixel-accessor.h in ImageMagick 7.0.3-8 allows remote attackers to cause a denial of service (out-of-bounds heap read) via a crafted image file.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2016-9556 represents a critical heap-based out-of-bounds read flaw within the ImageMagick library's pixel accessor functionality. This issue exists in the IsPixelGray function located in MagickCore/pixel-accessor.h, specifically affecting ImageMagick version 7.0.3-8. The vulnerability arises from inadequate input validation when processing specially crafted image files that manipulate pixel data structures. When an attacker submits a malformed image file to a system utilizing ImageMagick for image processing, the IsPixelGray function attempts to access heap memory beyond its allocated bounds, leading to unpredictable behavior and potential system instability.
The technical exploitation of this vulnerability demonstrates a classic buffer over-read condition that falls under CWE-125, which describes out-of-bounds read vulnerabilities in software systems. This flaw operates at the intersection of memory management and image processing protocols, where the application fails to properly validate the dimensions and structure of pixel data within image files. The heap read operation occurs when the function processes image metadata that does not conform to expected parameters, causing the program to access memory locations that may contain sensitive information or cause program termination. The vulnerability's remote nature means that attackers can trigger this condition through web applications or services that process user-uploaded images without proper sanitization.
The operational impact of CVE-2016-9556 extends beyond simple denial of service, as it can potentially lead to information disclosure or system compromise depending on the execution environment. Systems utilizing ImageMagick for image processing, including web applications, content management systems, and digital asset management platforms, become vulnerable to this attack vector. The out-of-bounds heap read could expose sensitive memory contents to attackers, potentially revealing cryptographic keys, user data, or system configuration details. This vulnerability directly maps to ATT&CK technique T1203, which involves the use of system exploitation to gain unauthorized access or cause denial of service conditions. The attack surface includes any application that accepts image uploads and processes them through ImageMagick's pixel accessor functions, making it particularly dangerous in web environments where user input is common.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected ImageMagick installations to version 7.0.3-9 or later, which contains the necessary fixes for the heap read condition. Organizations should implement comprehensive input validation and sanitization procedures for all image uploads, including MIME type checking, file size limits, and format verification. Network-level defenses such as web application firewalls can provide additional protection by filtering suspicious image file patterns before they reach backend processing systems. Security teams should also consider implementing sandboxing mechanisms that isolate image processing operations from critical system components, reducing the potential impact of successful exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify other potential heap-based memory issues within image processing libraries and ensure that all dependencies remain up-to-date with the latest security patches.