CVE-2016-5767 in GD Graphics Library
Summary
by MITRE
Integer overflow in the gdImageCreate function in gd.c in the GD Graphics Library (aka libgd) before 2.0.34RC1, as used in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8, allows remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via a crafted image dimensions.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability CVE-2016-5767 represents a critical integer overflow flaw within the GD Graphics Library, specifically in the gdImageCreate function located in gd.c. This library serves as a fundamental component for image processing in numerous web applications and programming environments, including PHP installations that were widely deployed across the internet. The flaw manifests when the library processes image dimensions that exceed the maximum value that can be represented by a signed integer, creating conditions where arithmetic operations produce unexpected results that can compromise memory integrity.
The technical implementation of this vulnerability stems from insufficient input validation within the image creation process. When PHP applications attempt to create images with dimensions that trigger integer overflow conditions, the library fails to properly handle the mathematical overflow that occurs during dimension calculations. This flaw falls under CWE-190, which specifically addresses integer overflow conditions, and represents a classic heap-based buffer overflow scenario where memory allocation calculations become corrupted. The vulnerability affects multiple PHP versions including 5.5.x before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8, indicating the widespread impact across the PHP ecosystem.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more sophisticated attack vectors. Remote attackers can craft malicious image files with deliberately oversized dimensions that, when processed by vulnerable systems, trigger heap corruption and application crashes. This creates significant risk for web applications that accept user-uploaded images or process external image sources, as the vulnerability can be exploited through simple HTTP requests without requiring authentication. The potential for unspecified other impacts suggests that in certain conditions, attackers might be able to execute arbitrary code or manipulate memory contents, making this a particularly dangerous vulnerability in web environments where image processing is common.
The attack surface for this vulnerability is extensive given the prevalence of PHP-based web applications and the widespread use of the GD library for image manipulation tasks. Systems that process user-generated content, image galleries, social media platforms, and any web application that handles image uploads are particularly vulnerable. The ATT&CK framework categorizes this as a resource exhaustion attack vector under the technique of "Resource Exhaustion" and potentially as "Code Injection" if the buffer overflow leads to memory corruption that can be exploited for code execution. Organizations should implement immediate mitigation strategies including updating to patched versions of both PHP and libgd, implementing strict image validation and dimension checking, and deploying web application firewalls to filter suspicious image content before it reaches vulnerable processing components.