CVE-2017-6502 in ImageMagick
Summary
by MITRE
An issue was discovered in ImageMagick 6.9.7. A specially crafted webp file could lead to a file-descriptor leak in libmagickcore (thus, a DoS).
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Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2017-6502 represents a critical file descriptor leak within ImageMagick's libmagickcore library version 6.9.7, specifically when processing specially crafted webp image files. This issue stems from inadequate resource management during image processing operations, where the library fails to properly close file descriptors after completing operations on maliciously formatted webp files. The flaw exists in the image parsing and handling mechanisms that do not adequately validate or sanitize input file structures before proceeding with resource allocation and processing tasks.
The technical implementation of this vulnerability involves the exploitation of improper resource cleanup routines within the webp decoder component of ImageMagick. When a malicious webp file is processed, the library allocates file descriptors to handle the image data but fails to release these descriptors upon completion of the parsing operation. This creates a resource exhaustion scenario where each processed malicious file consumes additional file descriptors without proper cleanup, leading to a gradual depletion of available file handles in the system. The vulnerability manifests as a denial of service condition because the application eventually exhausts its file descriptor limits and becomes unable to process additional image files or perform other file operations.
From an operational perspective, this vulnerability poses significant risks to systems that process untrusted image uploads or handle large volumes of webp image files. The DoS condition can be triggered through simple file upload attacks or by sending malicious webp files through email attachments, web forms, or file sharing systems. The impact extends beyond individual applications to potentially affect system stability, as file descriptor leaks can cause cascading failures in service availability. This vulnerability particularly affects web applications, content management systems, and any platform that relies on ImageMagick for image processing tasks, making it a critical concern for organizations maintaining public-facing image processing services.
The vulnerability aligns with CWE-404, which describes improper resource cleanup or release, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service attacks. Organizations should implement immediate mitigations including updating ImageMagick to versions that address this resource leak, implementing strict file validation and sanitization processes, and deploying monitoring systems to detect unusual file descriptor usage patterns. Additionally, system administrators should consider implementing resource limits and file descriptor quotas to prevent complete service exhaustion. The fix typically involves proper resource management practices including explicit file descriptor closure in error handling paths and implementing robust input validation that prevents malformed webp files from triggering the vulnerable code paths.