CVE-2017-11535 in ImageMagick
Summary
by MITRE
When ImageMagick 7.0.6-1 processes a crafted file in convert, it can lead to a heap-based buffer over-read in the WritePSImage() function in coders/ps.c.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability CVE-2017-11535 represents a critical heap-based buffer over-read flaw in ImageMagick version 7.0.6-1 that occurs during the processing of specially crafted image files through the convert command. This vulnerability specifically manifests within the WritePSImage() function located in the coders/ps.c source file, making it a significant concern for systems that handle image processing operations. The flaw stems from inadequate bounds checking during the handling of PostScript format output generation, where the software fails to properly validate the size of data being written to memory buffers. This issue directly maps to CWE-125, which describes out-of-bounds read vulnerabilities, and falls under the broader category of memory safety issues that have historically plagued image processing libraries. The vulnerability is particularly dangerous because it can be exploited through malicious file uploads or processing of untrusted image content, making it a prime target for remote code execution attacks when ImageMagick is used in web applications or automated processing pipelines.
The technical implementation of this vulnerability involves the improper handling of memory allocation when converting images to PostScript format. During the WritePSImage() function execution, ImageMagick attempts to write image data to a buffer without sufficient validation of the data size relative to the allocated memory space. This creates a scenario where a crafted input file can cause the software to read beyond the boundaries of allocated heap memory, potentially exposing sensitive data or causing application crashes. The vulnerability is triggered when the convert utility processes a specially constructed image file that contains malformed PostScript data, leading to the over-read condition in the memory management subsystem. This flaw demonstrates poor defensive programming practices and highlights the importance of input sanitization in multimedia processing applications, as the issue occurs during the conversion process rather than during initial file parsing, making detection more challenging in automated systems.
The operational impact of CVE-2017-11535 extends far beyond simple application instability, as it creates potential entry points for sophisticated attack vectors within web applications and server environments. Systems that rely on ImageMagick for image processing, including content management systems, file upload handlers, and automated image conversion services, become vulnerable to remote code execution when this flaw is exploited. Attackers can craft malicious image files that, when processed by vulnerable ImageMagick installations, trigger the buffer over-read condition and potentially allow arbitrary code execution with the privileges of the processing application. This vulnerability is particularly concerning in environments where ImageMagick is used in web contexts, as it can be exploited through simple file uploads without requiring additional authentication or complex attack chains. The implications align with ATT&CK technique T1059.007, which covers command and scripting interpreter usage, as successful exploitation could enable attackers to execute shell commands through the compromised image processing pipeline.
Mitigation strategies for CVE-2017-11535 should focus on immediate patching of affected ImageMagick versions, along with implementation of additional security controls to reduce attack surface. Organizations should upgrade to ImageMagick version 7.0.6-10 or later, which contains the necessary fixes for this vulnerability. Beyond patching, system administrators should implement strict file validation and sanitization measures, including MIME type checking, file extension validation, and content-based file analysis before processing. Network-level protections such as web application firewalls and content filtering systems can help detect and block malicious file uploads that might exploit this vulnerability. The remediation approach should also include disabling unnecessary image format support in ImageMagick installations, particularly for PostScript-related formats when not required. Regular security assessments and vulnerability scanning should be conducted to identify other potential weaknesses in image processing pipelines, as this vulnerability demonstrates how seemingly benign file processing operations can become attack vectors in modern web applications. The fix implemented by ImageMagick developers addresses the root cause by adding proper bounds checking in the WritePSImage() function, ensuring that memory operations remain within allocated buffer boundaries and preventing the over-read condition from occurring.