CVE-2018-6405 in ImageMagick
Summary
by MITRE
In the ReadDCMImage function in coders/dcm.c in ImageMagick before 7.0.7-23, each redmap, greenmap, and bluemap variable can be overwritten by a new pointer. The previous pointer is lost, which leads to a memory leak. This allows remote attackers to cause a denial of service.
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Analysis
by VulDB Data Team • 02/03/2023
The vulnerability identified as CVE-2018-6405 resides within the ReadDCMImage function of ImageMagick's DICOM coder implementation, specifically in the coders/dcm.c file. This issue affects versions prior to 7.0.7-23 and represents a classic memory management flaw that can be exploited remotely to cause denial of service conditions. The vulnerability manifests when processing DICOM (Digital Imaging and Communications in Medicine) image files, which are commonly used in medical imaging environments and healthcare systems. The flaw occurs during the parsing of medical image metadata where the software handles color mapping information through redmap, greenmap, and bluemap variables that are responsible for storing color palette data.
The technical root cause of this vulnerability stems from improper pointer management within the image processing pipeline. When the ReadDCMImage function processes DICOM files, it allocates memory for color mapping arrays and assigns pointers to these memory regions. However, the implementation fails to properly handle cases where these pointer variables receive new assignments without first releasing the previously allocated memory. This results in a memory leak scenario where the original memory allocations become unreachable but remain allocated, creating a gradual consumption of system resources. The vulnerability is classified as a memory leak under CWE-401, which specifically addresses the failure to release memory after it is no longer needed. The flaw is particularly concerning because it can be triggered through the processing of maliciously crafted DICOM files, making it a remote attack vector that does not require local system access.
The operational impact of CVE-2018-6405 extends beyond simple resource exhaustion, as it can severely compromise the availability of systems that process medical imaging data. Healthcare environments that rely on ImageMagick for image processing, viewing, or conversion tasks become vulnerable to denial of service attacks that can render critical systems unusable. Attackers can exploit this vulnerability by uploading or transmitting specially crafted DICOM files that, when processed by vulnerable ImageMagick installations, cause progressive memory consumption until system resources are exhausted. This makes the vulnerability particularly dangerous in environments where ImageMagick is used as part of automated workflows or web services that handle medical image processing. The attack vector aligns with ATT&CK technique T1499.004, which focuses on network denial of service attacks, and demonstrates how memory management flaws can be leveraged to create persistent availability issues. The vulnerability affects systems across various deployment scenarios including web applications, medical imaging workstations, and automated processing pipelines that utilize ImageMagick for DICOM file handling.
The remediation strategy for CVE-2018-6405 requires immediate patching of ImageMagick installations to version 7.0.7-23 or later, which contains the necessary fixes for proper pointer management. Organizations should conduct comprehensive vulnerability assessments to identify all systems running vulnerable versions of ImageMagick, particularly those handling medical imaging data or processing files from untrusted sources. Network segmentation and input validation controls should be implemented to prevent unauthorized file uploads or processing of potentially malicious DICOM files. Security monitoring should be enhanced to detect unusual memory consumption patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing sandboxing mechanisms for image processing tasks and establishing regular patch management procedures to ensure timely deployment of security updates. The fix addresses the underlying memory leak by ensuring proper pointer cleanup and memory deallocation before new assignments are made, thereby preventing the accumulation of unreferenced memory blocks that characterize this type of vulnerability. This remediation aligns with security best practices outlined in NIST SP 800-128 and follows the principle of least privilege by limiting the memory footprint of image processing operations.