CVE-2017-6363 in GD Graphics Library
Summary
by MITRE
** DISPUTED ** In the GD Graphics Library (aka LibGD) through 2.2.5, there is a heap-based buffer over-read in tiffWriter in gd_tiff.c. NOTE: the vendor says "In my opinion this issue should not have a CVE, since the GD and GD2 formats are documented to be 'obsolete, and should only be used for development and testing purposes.'"
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Analysis
by VulDB Data Team • 04/27/2025
The vulnerability identified as CVE-2017-6363 affects the GD Graphics Library version 2.2.5 and earlier, specifically within the tiffWriter function located in the gd_tiff.c source file. This represents a heap-based buffer over-read condition that occurs when processing TIFF image files, making it a critical security concern for systems that handle untrusted image data. The issue manifests when the library attempts to write TIFF format data to memory, exceeding the allocated buffer boundaries and potentially leading to memory corruption or information disclosure. The vulnerability is classified under CWE-125 as an out-of-bounds read, which can result in unpredictable behavior and system instability. According to the ATT&CK framework, this vulnerability could be leveraged in initial access or execution phases where adversaries might attempt to exploit image processing functions to gain unauthorized access to systems.
The technical flaw in this vulnerability stems from inadequate bounds checking within the TIFF writing functionality of the GD library. When the tiffWriter function processes image data for TIFF format output, it fails to properly validate the size of data being written to allocated memory buffers, allowing for data to be written beyond the intended buffer limits. This over-read condition can occur when the library handles certain TIFF image structures or metadata that exceed expected buffer dimensions, potentially causing the program to read memory locations that do not belong to the allocated buffer. The heap-based nature of the vulnerability means that the memory corruption occurs in the heap segment of the program's memory space, making it particularly dangerous as it can lead to arbitrary code execution or system crashes. The vulnerability exists in the context of image processing libraries that are widely used in web applications and content management systems, creating a broad attack surface.
The operational impact of CVE-2017-6363 extends beyond simple memory corruption, potentially enabling attackers to exploit the vulnerability through image file manipulation in web applications that utilize the GD library for image processing. Systems using vulnerable versions of the GD library could be targeted through malicious TIFF files uploaded to web applications, leading to remote code execution or denial of service conditions. The vendor's statement that the GD and GD2 formats should only be used for development and testing purposes underscores the inherent risks associated with these legacy formats, as they were never intended for production use in security-sensitive environments. This vulnerability demonstrates the ongoing risks associated with supporting deprecated image formats and highlights the importance of proper input validation in graphics processing libraries. The impact is particularly concerning in web environments where users might upload arbitrary image files, as the vulnerability can be exploited through simple file uploads without requiring special privileges or complex attack vectors.
Mitigation strategies for this vulnerability involve immediate upgrades to GD Graphics Library version 2.2.6 or later, which contains the necessary fixes for the buffer over-read issue. Organizations should also implement strict input validation for all image file processing, particularly for TIFF format files, and consider disabling support for legacy image formats in production environments where possible. The implementation of memory protection mechanisms such as stack canaries, address space layout randomization, and heap integrity checks can provide additional layers of defense against exploitation attempts. Security teams should also conduct comprehensive vulnerability assessments of systems that utilize the GD library, particularly focusing on web applications and services that handle user-uploaded image files. The vulnerability serves as a reminder of the importance of regularly updating third-party libraries and maintaining current security patches, as legacy formats and functions often present overlooked security risks. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, and establish monitoring procedures to detect unusual image processing activities that might indicate exploitation attempts.