CVE-2013-7456 in GD Graphics Library
Summary
by MITRE
gd_interpolation.c in the GD Graphics Library (aka libgd) before 2.1.1, as used in PHP before 5.5.36, 5.6.x before 5.6.22, and 7.x before 7.0.7, allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted image that is mishandled by the imagescale function.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2013-7456 represents a critical out-of-bounds read flaw within the GD Graphics Library, specifically affecting the gd_interpolation.c component. This vulnerability impacts a wide range of PHP versions including those before 5.5.36, 5.6.x before 5.6.22, and 7.x before 7.0.7, making it particularly dangerous due to the widespread use of PHP in web applications. The flaw occurs when the imagescale function processes crafted image files, creating conditions where memory access violations can occur. The vulnerability is classified under CWE-125 as an out-of-bounds read, which can lead to information disclosure, system instability, or potentially more severe consequences depending on the execution environment.
The technical implementation of this vulnerability stems from inadequate input validation within the image scaling functionality of libgd. When PHP processes images through the imagescale function, it relies on the underlying GD library to handle various image manipulation operations. The flaw manifests when malformed image data is passed to this function, causing the interpolation algorithm to access memory locations beyond the allocated buffer boundaries. This occurs because the library fails to properly validate the dimensions and parameters of input images before performing scaling operations, allowing attackers to craft malicious image files that trigger buffer overread conditions.
From an operational standpoint, this vulnerability presents significant risks to web application security and system stability. Remote attackers can exploit this flaw by uploading or otherwise providing maliciously crafted image files to systems running vulnerable PHP versions. The out-of-bounds read can result in denial of service conditions where the application crashes or becomes unresponsive, but more concerning is the potential for information disclosure where sensitive memory contents may be exposed to attackers. The unspecified other impacts mentioned in the vulnerability description suggest that under certain conditions, this flaw could potentially be leveraged for more sophisticated attacks including privilege escalation or code execution.
The attack surface for this vulnerability is extensive given the prevalence of PHP in web environments and the common use of image processing functions in web applications. Systems running vulnerable versions of PHP are particularly at risk when they accept user-uploaded images or process images from external sources without proper validation. The vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, as it enables attackers to execute malicious code through compromised image processing functions. Additionally, it relates to T1068 - Exploitation for Privilege Escalation when the affected applications run with elevated privileges, potentially allowing attackers to gain unauthorized access to system resources.
Mitigation strategies for CVE-2013-7456 primarily involve immediate patching of affected systems with updated versions of PHP and the GD Graphics Library. Organizations should prioritize updating to PHP versions 5.5.36, 5.6.22, or 7.0.7 respectively, which contain the necessary fixes for this vulnerability. Beyond patching, implementing proper image validation and sanitization measures can provide additional defense-in-depth. Web applications should validate image file types, dimensions, and content before processing them through image scaling functions. Input validation should include checking for malformed image headers, unusual dimensions, and other suspicious characteristics that might indicate crafted malicious content. Organizations should also consider implementing network segmentation and monitoring for unusual image processing activities that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date graphics libraries and image processing components in web applications, as these libraries often serve as attack vectors for broader system compromise.