CVE-2016-6161 in GD Graphics Library
Summary
by MITRE
The output function in gd_gif_out.c in the GD Graphics Library (aka libgd) allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted image.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability identified as CVE-2016-6161 resides within the GD Graphics Library, specifically in the gd_gif_out.c component responsible for handling gif image output operations. This flaw represents a critical security issue that affects numerous applications and systems relying on libgd for image processing tasks. The vulnerability manifests as an out-of-bounds read condition that can be exploited by remote attackers through the careful crafting of malicious image files. Such a vulnerability falls under the category of memory safety issues and aligns with CWE-125, which describes out-of-bounds read conditions that can lead to unpredictable behavior and potential system compromise. The GD Graphics Library serves as a fundamental component in many web applications, content management systems, and image processing frameworks, making this vulnerability particularly dangerous as it can affect a wide range of software ecosystems.
The technical implementation of this vulnerability stems from insufficient validation of input parameters during gif image processing operations. When the output function processes a malformed gif image, it fails to properly bounds-check array accesses or validate image structure elements before attempting to read data from memory locations that may extend beyond the allocated buffer boundaries. This improper handling allows attackers to craft specially designed gif files that trigger memory access violations when processed by applications using libgd. The out-of-bounds read occurs during the gif encoding process when the library attempts to access pixel data or metadata structures that have not been properly validated or sanitized. The vulnerability is particularly concerning because it can be triggered remotely through web applications that accept image uploads or process external image sources without proper input sanitization.
The operational impact of CVE-2016-6161 extends beyond simple denial of service conditions to potentially enable more sophisticated attack vectors. While the primary effect is a denial of service through system crashes or resource exhaustion, the underlying memory safety issue creates opportunities for information disclosure or even arbitrary code execution in certain scenarios. Remote attackers can leverage this vulnerability to disrupt services by causing application crashes or system instability, effectively creating a denial of service condition that impacts availability. The vulnerability's exploitation potential increases when applications using libgd fail to implement proper input validation or when they process images from untrusted sources without adequate security measures. This flaw can be particularly damaging in web applications where users can upload images, as it provides an attack surface that can be exploited to compromise entire application servers or web services. The attack can be executed through standard web requests, making it easily accessible to threat actors without requiring special privileges or complex attack chains.
Mitigation strategies for CVE-2016-6161 should focus on immediate patching of affected libgd versions, implementing proper input validation at application level, and deploying defensive measures such as web application firewalls. Organizations should prioritize upgrading to patched versions of the GD Graphics Library, as version 2.1.3 and later contain fixes for this vulnerability. Additionally, implementing strict input validation and sanitization for all image uploads, particularly those processed through libgd, can prevent exploitation attempts. Security measures should include validating image file headers, implementing size limits for uploaded images, and using sandboxed environments for image processing operations. From a defensive perspective, implementing network monitoring to detect suspicious image processing requests and deploying intrusion detection systems can help identify exploitation attempts. The vulnerability also highlights the importance of following secure coding practices and conducting regular security assessments of third-party libraries. Organizations should consider implementing automated vulnerability scanning tools that can detect the presence of vulnerable library versions and ensure proper patch management protocols are in place to maintain system security. The remediation process should also include comprehensive testing to ensure that patched versions do not introduce regressions in existing functionality while maintaining the security improvements.