CVE-2018-15879 in GD Graphics Library
Summary
by MITRE
The GD Graphics Library (aka libgd) through 2.2.5 has a Double Free Vulnerability in the gdImageBmpPt function.
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Analysis
by VulDB Data Team • 10/07/2023
The GD Graphics Library represents a widely-used open-source software library for creating and manipulating raster graphics, particularly within web applications and server-side image processing environments. This library serves as a foundational component for numerous web platforms, content management systems, and image handling applications across various operating systems and programming languages. The vulnerability identified as CVE-2018-15879 specifically targets version 2.2.5 and earlier of this graphics library, affecting systems that process bitmap image data through the gdImageBmpPt function. This flaw exists within the library's memory management routines when handling certain malformed bitmap image inputs, creating a critical security risk that can be exploited across multiple deployment scenarios.
The technical flaw manifests as a double free vulnerability within the gdImageBmpPt function, which is responsible for processing bitmap image data points. When processing malformed bitmap images, the library's memory allocation and deallocation routines fail to properly track memory references, leading to situations where the same memory block gets freed twice. This occurs due to inadequate validation of input parameters and improper handling of memory cleanup operations within the bitmap processing pipeline. The vulnerability stems from a classic memory safety issue where the library's internal memory management code does not properly validate the state of allocated memory blocks before attempting deallocation operations, creating conditions where memory corruption can occur. This type of vulnerability falls under CWE-415, which specifically addresses double free conditions in memory management, and represents a fundamental flaw in the library's defensive programming practices.
The operational impact of this vulnerability extends across numerous attack vectors and deployment scenarios where the affected library is utilized. Web applications that accept user-uploaded images, content management systems, image processing services, and server-side applications that handle bitmap graphics are all at risk when running vulnerable versions of libgd. An attacker can craft specially malformed bitmap images that trigger the double free condition when processed by the library, potentially leading to arbitrary code execution, denial of service, or information disclosure. The vulnerability can be exploited through various attack paths including file upload restrictions bypass, web application exploitation, and remote code execution scenarios, making it particularly dangerous in multi-tenant environments where untrusted image inputs are processed. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1059 for command and control, and T1499 for endpoint denial of service, as it can enable both persistent access and service disruption.
Mitigation strategies for this vulnerability require immediate patching of affected systems with the latest stable versions of libgd, specifically versions 2.2.6 and later which contain the necessary memory management fixes. Organizations should implement comprehensive input validation and sanitization for all image processing operations, including MIME type checking, file size limits, and format validation. Network segmentation and access controls should be enforced to limit exposure of systems that process user-uploaded content, while implementing robust monitoring and logging of image processing activities to detect potential exploitation attempts. Additionally, application-level defenses such as sandboxing image processing operations, implementing strict memory limits, and deploying intrusion detection systems can provide additional layers of protection. The vulnerability serves as a critical reminder of the importance of regular security updates, proper input validation, and memory safety practices in graphics processing libraries, particularly those used in high-risk web applications where untrusted inputs are processed.