CVE-2016-7568 in GD Graphics Library
Summary
by MITRE
Integer overflow in the gdImageWebpCtx function in gd_webp.c in the GD Graphics Library (aka libgd) through 2.2.3, as used in PHP through 7.0.11, allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via crafted imagewebp and imagedestroy calls.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability CVE-2016-7568 represents a critical integer overflow flaw within the GD Graphics Library's webp image processing functionality. This vulnerability exists in the gdImageWebpCtx function located in gd_webp.c file of libgd versions up to 2.2.3, which is widely integrated into PHP versions through 7.0.11. The flaw manifests when processing specially crafted webp image data through the imagewebp and imagedestroy PHP functions, creating a heap-based buffer overflow condition that can be exploited remotely by attackers. The vulnerability falls under CWE-190, which specifically addresses integer overflow conditions, and can be categorized under the ATT&CK technique T1499.3 for denial of service attacks. The integer overflow occurs during the calculation of buffer sizes required for webp image processing, where malicious input causes arithmetic operations to produce values that exceed the maximum representable integer, leading to improper memory allocation.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. When an attacker successfully exploits this integer overflow, they can manipulate heap memory layout through crafted webp image data, potentially leading to arbitrary code execution or information disclosure depending on the target system's memory protection mechanisms. The vulnerability affects web applications that process user-uploaded webp images or those that accept webp image data from external sources, making it particularly dangerous in web server environments where image processing is common. The heap-based buffer overflow creates memory corruption that can be leveraged to overwrite adjacent memory locations, potentially allowing attackers to modify program execution flow or extract sensitive information from memory. This makes the vulnerability particularly concerning for web applications that process untrusted image data, as the attack surface includes any application using the affected PHP versions with GD library integration.
Mitigation strategies for CVE-2016-7568 require immediate patching of affected systems and implementation of defensive measures. Organizations should prioritize updating their PHP installations to versions 7.0.12 or later, where the vulnerability has been patched, and ensure the GD library is updated to version 2.2.4 or higher. Additionally, implementing input validation and sanitization for all image uploads, including webp format files, can provide defense-in-depth protection. Web applications should validate image dimensions and file sizes before processing, and consider implementing resource limits on image processing operations to prevent exploitation attempts. The vulnerability demonstrates the importance of proper integer overflow checking in memory allocation functions, and organizations should review their image processing libraries for similar issues. Security monitoring should include detection of unusual memory allocation patterns or potential buffer overflow attempts, while network-level defenses can be enhanced to filter suspicious image file uploads. The ATT&CK framework suggests implementing application whitelisting and runtime application control to prevent exploitation of such vulnerabilities in environments where immediate patching is not feasible.