CVE-2018-20189 in GraphicsMagick
Summary
by MITRE
In GraphicsMagick 1.3.31, the ReadDIBImage function of coders/dib.c has a vulnerability allowing a crash and denial of service via a dib file that is crafted to appear with direct pixel values and also colormapping (which is not available beyond 8-bits/sample), and therefore lacks indexes initialization.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-20189 affects GraphicsMagick version 1.3.31 and resides within the ReadDIBImage function located in the coders/dib.c file. This issue represents a critical flaw in how the software processes Device Independent Bitmap (DIB) image files, specifically when handling files that contain both direct pixel values and colormapping information simultaneously. The vulnerability stems from an insufficient validation mechanism that fails to properly initialize index values when processing DIB files with high bit-depth characteristics beyond 8 bits per sample. This particular configuration creates a scenario where the application attempts to access memory locations without proper initialization, leading to unpredictable behavior and system instability.
The technical nature of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-476, which covers null pointer dereference scenarios. When a maliciously crafted DIB file is processed, the ReadDIBImage function encounters a conflict between direct pixel value representation and colormapping structures that cannot coexist effectively beyond 8 bits per sample. The function fails to properly initialize the index mapping required for high-bit-depth color representation, causing memory access violations that result in application crashes and potential denial of service conditions. This flaw operates at the intersection of image format parsing and memory management, making it particularly dangerous as it can be triggered through simple file processing operations without requiring specialized privileges or complex attack vectors.
From an operational impact perspective, this vulnerability presents significant risks to systems that rely on GraphicsMagick for image processing tasks, particularly in web applications, content management systems, and automated image handling workflows. The denial of service aspect means that legitimate users may experience service interruptions when the application processes compromised image files, while the crash potential could lead to complete application termination and system instability. Attackers could exploit this vulnerability by uploading or providing malicious DIB files to systems that process such images, potentially causing cascading failures in larger networked environments where GraphicsMagick serves as a critical component in image processing pipelines. The vulnerability's impact extends beyond simple crashes to encompass broader system availability concerns, making it particularly concerning for services that depend on continuous image processing capabilities.
The recommended mitigations for this vulnerability include immediate upgrade to GraphicsMagick version 1.3.32 or later, where the issue has been addressed through proper index initialization and enhanced validation of DIB file structures. Organizations should implement strict file validation procedures that verify image format integrity before processing, particularly for user-uploaded content or external image sources. Additionally, deploying network-based intrusion detection systems that can identify and block suspicious image file patterns may provide additional protective layers. The fix implemented by the GraphicsMagick development team specifically addresses the root cause by ensuring proper initialization of color mapping indexes when processing DIB files, preventing the out-of-bounds memory access that previously occurred. Security teams should also consider implementing sandboxed environments for image processing tasks and establishing comprehensive monitoring protocols to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management in multimedia processing libraries, particularly when handling complex file formats that may contain conflicting data structures. Organizations using GraphicsMagick should conduct thorough vulnerability assessments to identify all systems that may be exposed to this issue and implement layered security approaches to minimize potential impact from similar future vulnerabilities.