CVE-2016-6905 in GD Graphics Library
Summary
by MITRE
The read_image_tga function in gd_tga.c in the GD Graphics Library (aka libgd) before 2.2.3 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted TGA image.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-6905 affects the GD Graphics Library version 2.2.2 and earlier, specifically within the read_image_tga function located in gd_tga.c. This flaw represents a critical security issue that enables remote attackers to execute a denial of service attack through out-of-bounds memory reads. The GD Graphics Library serves as a popular graphics library for creating and manipulating images, widely used in web applications and server-side image processing systems. When processing specially crafted TGA image files, the library fails to properly validate input data, leading to memory access violations that can crash applications or cause system instability. The vulnerability stems from insufficient bounds checking during the parsing of TGA file headers and image data structures, allowing attackers to craft malicious files that trigger memory access beyond allocated buffers. This issue falls under the Common Weakness Enumeration category CWE-125, which identifies out-of-bounds read vulnerabilities as a fundamental flaw in memory safety mechanisms. The attack vector is particularly concerning as it can be exploited remotely through web applications that utilize the GD library for image processing, making it a significant threat to web server security. The operational impact extends beyond simple service disruption, as the vulnerability can be leveraged to crash web applications, potentially leading to complete system unavailability and affecting multiple users simultaneously.
The technical implementation of this vulnerability demonstrates a classic buffer over-read scenario where the read_image_tga function does not adequately validate the dimensions and data structure of incoming TGA files. When a malicious TGA file is processed, the function attempts to read memory locations that are outside the bounds of allocated buffers, causing unpredictable behavior and potential system crashes. The flaw occurs during the parsing of TGA file headers, where the library assumes certain field values will be within expected ranges without proper validation. This lack of input sanitization creates an opportunity for attackers to craft TGA files with malformed header values that cause the library to read beyond the actual file boundaries. The vulnerability can be exploited through various attack vectors including web uploads, image processing APIs, and any application that accepts TGA format images from untrusted sources. The out-of-bounds read condition can be triggered regardless of the operating system or platform, making it particularly dangerous in multi-platform environments. Security researchers have noted that this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and T1059.007, covering scripting through command-line interpreters, as the vulnerability can be exploited through automated scripts that generate malicious TGA files.
Mitigation strategies for CVE-2016-6905 primarily focus on updating to the patched version of the GD Graphics Library, specifically version 2.2.3 or later, which includes proper bounds checking and input validation mechanisms. System administrators should prioritize patching all affected applications and services that utilize the GD library for image processing, particularly web applications, content management systems, and any server-side image manipulation tools. Organizations should implement additional protective measures such as input validation at the application level, file type verification, and content filtering to prevent malicious TGA files from reaching the GD library processing functions. Network-level protections including firewall rules and intrusion detection systems can help monitor for suspicious file upload activities and potentially malicious TGA file patterns. Security teams should also consider implementing sandboxing techniques for image processing operations to contain potential exploitation attempts. The vulnerability highlights the importance of comprehensive input validation and memory safety practices in graphics processing libraries, as similar issues have been identified in other image processing libraries and multimedia frameworks. Regular security assessments and vulnerability scanning should include checks for outdated GD library versions, and organizations should maintain updated inventories of all software components that may be vulnerable to similar issues. The remediation process should also include thorough testing of patched applications to ensure that the update does not introduce compatibility issues with existing image processing workflows while effectively addressing the denial of service vulnerability.