CVE-2017-9727 in Ghostscript GhostXPS
Summary
by MITRE
The gx_ttfReader__Read function in base/gxttfb.c in Artifex Ghostscript GhostXPS 9.22 allows remote attackers to cause a denial of service (heap-based buffer over-read and application crash) or possibly have unspecified other impact via a crafted document.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-9727 affects Artifex Ghostscript GhostXPS version 9.22 and resides within the gx_ttfReader__Read function located in base/gxttfb.c. This flaw represents a heap-based buffer over-read condition that can be exploited by remote attackers through the careful crafting of malicious documents. The issue stems from insufficient input validation and boundary checking when processing TrueType font data within XPS document parsing operations. When a malicious document is processed, the function attempts to read beyond the allocated heap memory boundaries, leading to unpredictable behavior and system instability.
The technical exploitation of this vulnerability involves manipulating the font processing logic to trigger an out-of-bounds memory read operation. The heap-based buffer over-read occurs during the parsing of TrueType font tables where the application fails to properly validate the size parameters of font data structures. This type of vulnerability falls under CWE-125, which specifically addresses out-of-bounds read conditions in software implementations. The vulnerability can be classified as a remote code execution risk due to the potential for arbitrary code execution through memory corruption, though the immediate impact manifests as denial of service through application crashes.
From an operational perspective, this vulnerability creates significant risks for organizations that process untrusted XPS documents or PDF files containing embedded fonts. The impact extends beyond simple denial of service as the heap corruption could potentially be leveraged for more sophisticated attacks if combined with other vulnerabilities. The vulnerability affects systems that rely on Ghostscript for document processing, particularly those handling email attachments, document sharing platforms, or print server environments where users might encounter maliciously crafted documents. The ATT&CK framework categorizes this as a privilege escalation or code execution technique through software exploitation, specifically targeting the application layer of system security.
Mitigation strategies for CVE-2017-9727 should prioritize immediate patching of affected Ghostscript installations to version 9.23 or later where the vulnerability has been addressed. Organizations should implement strict document validation policies and consider sandboxing document processing environments to limit potential impact. Network segmentation and access controls can help prevent unauthorized users from submitting malicious documents to processing systems. Additionally, monitoring for unusual application crashes or memory access patterns can serve as early detection mechanisms for exploitation attempts. The vulnerability demonstrates the importance of robust input validation in font parsing libraries and highlights the need for comprehensive memory safety testing in document processing software.