CVE-2017-18231 in GraphicsMagick
Summary
by MITRE
An issue was discovered in GraphicsMagick 1.3.26. A NULL pointer dereference vulnerability was found in the function ReadEnhMetaFile in coders/emf.c, which allows attackers to cause a denial of service via a crafted file.
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Analysis
by VulDB Data Team • 09/12/2024
The vulnerability identified as CVE-2017-18231 represents a critical null pointer dereference flaw within GraphicsMagick version 1.3.26, specifically within the ReadEnhMetaFile function located in the coders/emf.c source file. This issue stems from inadequate input validation and error handling mechanisms that fail to properly check for null pointer conditions during the processing of enhanced metafile format files. The flaw manifests when the software attempts to dereference a pointer that has not been properly initialized or validated, creating a condition where the application crashes upon encountering malformed input data. Such vulnerabilities fall under the category of CWE-476_NULL_Pointer_Dereference, which is classified as a fundamental weakness in software design that directly impacts system stability and availability. The vulnerability is particularly concerning because it can be exploited through crafted file inputs that manipulate the Enhanced Metafile (EMF) format processing pipeline, making it a prime target for denial of service attacks.
The technical exploitation of this vulnerability occurs when GraphicsMagick processes an intentionally malformed EMF file that triggers the null pointer dereference within the ReadEnhMetaFile function. During normal operation, the software expects certain pointer values to be properly initialized before dereferencing them, but in the presence of crafted input data, these pointers remain null or uninitialized. The function fails to implement proper defensive programming practices such as null pointer checks before memory access operations, which is a common pattern in buffer overflow and denial of service vulnerabilities. This specific flaw demonstrates poor error handling within the graphics processing library, where the software does not adequately validate the integrity of input files before attempting to parse and process their contents. The attack vector is particularly effective because EMF files are commonly used in Windows environments and can be embedded in various document formats, making them a viable attack surface for remote exploitation.
The operational impact of CVE-2017-18231 extends beyond simple denial of service, as it can significantly disrupt system availability and potentially provide attackers with opportunities to escalate their attacks. When exploited, this vulnerability causes the GraphicsMagick process to crash and terminate unexpectedly, leading to service disruption for applications that depend on this library for image processing tasks. The vulnerability is particularly dangerous in server environments where GraphicsMagick is used as part of web applications, content management systems, or document processing pipelines, as it can be leveraged to create persistent denial of service conditions. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion or application crashes. The vulnerability's impact is amplified when considering that GraphicsMagick is widely used across various platforms and applications, meaning a single exploit could potentially affect multiple systems simultaneously.
Mitigation strategies for CVE-2017-18231 should prioritize immediate patching of affected systems with the latest GraphicsMagick releases that contain the necessary code fixes for null pointer validation. Organizations should implement input validation measures that sanitize all file inputs before processing, particularly those related to EMF and other graphics formats, through the use of file type detection and content validation mechanisms. Network-level protections such as intrusion prevention systems can be configured to detect and block suspicious file upload patterns that might indicate exploitation attempts. Additionally, implementing application sandboxing and privilege separation techniques can limit the potential damage from successful exploitation attempts. Security monitoring should include detection of unusual process termination patterns and service disruptions related to image processing functions. The fix for this vulnerability typically involves adding proper null pointer checks within the ReadEnhMetaFile function and ensuring that all pointer variables are properly initialized before use, which directly addresses the underlying CWE-476 weakness and prevents the exploitation scenario from succeeding. Organizations should also consider implementing automated vulnerability scanning and patch management processes to prevent similar issues from affecting other components in their software stack.