CVE-2016-10218 in Ghostscript
Summary
by MITRE
The pdf14_pop_transparency_group function in base/gdevp14.c in the PDF Transparency module in Artifex Software, Inc. Ghostscript 9.20 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted file.
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Analysis
by VulDB Data Team • 11/24/2022
The vulnerability identified as CVE-2016-10218 resides within the PDF Transparency module of Ghostscript version 9.20, specifically in the pdf14_pop_transparency_group function located in base/gdevp14.c. This issue represents a critical denial of service vulnerability that can be exploited by remote attackers through the careful crafting of malicious PDF files. The flaw manifests as a NULL pointer dereference condition that leads to application crashes, effectively rendering the affected system unusable for legitimate PDF processing tasks. Artifex Software Inc. developed Ghostscript as a comprehensive PostScript and PDF interpreter, making this vulnerability particularly concerning given the widespread use of PDF processing in enterprise environments and web applications.
The technical nature of this vulnerability stems from insufficient input validation within the transparency group handling mechanism of the PDF rendering engine. When the pdf14_pop_transparency_group function processes malformed transparency group data structures in PDF files, it fails to properly check for null pointers before dereferencing them. This classic programming error falls under CWE-476, which specifically addresses NULL pointer dereference conditions that can lead to application instability and crashes. The vulnerability demonstrates a fundamental flaw in the defensive programming practices employed within the PDF transparency module, where proper error handling and input sanitization mechanisms are absent or inadequate.
The operational impact of CVE-2016-10218 extends beyond simple service disruption, as it can be leveraged by attackers to create persistent denial of service conditions against systems processing PDF documents. In enterprise environments where PDF handling is integral to document management, email processing, and web application workflows, this vulnerability can result in significant operational downtime and productivity losses. The remote exploitability aspect means that attackers can trigger the vulnerability without requiring physical access to the target system, making it particularly dangerous for web-facing applications that process user-uploaded PDF files. Security professionals should note that this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, as the exploitation results in application unavailability and service disruption.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected Ghostscript installations to version 9.21 or later, where the NULL pointer dereference has been addressed through proper input validation and error handling mechanisms. Organizations should also implement defensive measures such as PDF file validation and sanitization processes before processing documents, particularly for files received from untrusted sources. Network-based protections including web application firewalls and content filtering systems can help detect and block malicious PDF files that may contain the crafted transparency group data structures designed to trigger this vulnerability. Additionally, security teams should conduct regular vulnerability assessments to identify other potential NULL pointer dereference issues within similar PDF processing libraries and ensure proper input validation practices are maintained throughout the software development lifecycle to prevent similar issues from emerging in future releases.