CVE-2018-16643 in ImageMagick
Summary
by MITRE
The functions ReadDCMImage in coders/dcm.c, ReadPWPImage in coders/pwp.c, ReadCALSImage in coders/cals.c, and ReadPICTImage in coders/pict.c in ImageMagick 7.0.8-4 do not check the return value of the fputc function, which allows remote attackers to cause a denial of service via a crafted image file.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16643 represents a critical denial of service flaw within ImageMagick's image processing libraries, specifically affecting versions up to 7.0.8-4. This issue manifests in four distinct coder functions that handle different image formats including DICOM, PWP, CALS, and PICT file types. The flaw occurs when these functions fail to validate the return values from the fputc system call, creating a potential attack vector that remote adversaries can exploit through specially crafted image files. The absence of proper error checking in these critical functions allows attackers to manipulate the application's behavior and potentially disrupt service availability.
The technical root cause of this vulnerability stems from inadequate error handling practices within the image processing pipeline. When the fputc function is called to write a single character to a file stream, it returns an integer value indicating success or failure of the operation. In the affected ImageMagick versions, the return value is completely ignored, meaning that if the write operation fails due to insufficient disk space, permission issues, or other I/O problems, the application continues execution without detecting the failure. This oversight creates a scenario where the application may appear to function normally while silently failing to complete critical file operations, ultimately leading to application instability or complete termination.
From an operational perspective, this vulnerability presents a significant risk to systems that process untrusted image files, particularly those running ImageMagick in web applications, content management systems, or file processing services. Attackers can craft malicious image files that trigger the flawed code paths, causing the application to crash or become unresponsive. The denial of service impact is particularly concerning in environments where ImageMagick is used as a backend service, as it could lead to complete service disruption for legitimate users. The vulnerability demonstrates a classic example of how seemingly minor error handling oversights can result in severe operational consequences, especially when applications process files from untrusted sources.
The vulnerability aligns with CWE-704, which categorizes improper error handling and failure to check return values as a common weakness in software security practices. From an attacker's perspective, this flaw maps to ATT&CK technique T1499.004, which involves network denial of service attacks through the exploitation of application vulnerabilities. The attack surface is particularly broad given that ImageMagick is widely deployed across various platforms and applications, making the impact of this vulnerability widespread. Organizations using ImageMagick in production environments should consider this vulnerability as a high-priority concern, especially in systems where image processing is a core function and where untrusted input is accepted.
Mitigation strategies for CVE-2018-16643 primarily involve updating to patched versions of ImageMagick where the return values from fputc operations are properly validated. System administrators should also implement proper input validation and sanitization measures when processing image files, including limiting file sizes, implementing strict format validation, and using sandboxed environments for image processing tasks. Additional protective measures include monitoring for unusual application behavior, implementing resource limits to prevent exhaustion attacks, and maintaining regular security updates for all image processing libraries in use. The vulnerability serves as a reminder of the importance of comprehensive error handling in security-critical applications and the potential consequences of overlooking fundamental safety checks in file processing operations.