CVE-2017-9619 in Ghostscript GhostXPS
Summary
by MITRE
The xps_true_callback_glyph_name function in xps/xpsttf.c in Artifex Ghostscript GhostXPS 9.22 allows remote attackers to cause a denial of service (Segmentation Violation and application crash) via a crafted file.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-9619 resides within the GhostXPS component of Artifex Ghostscript version 9.22, specifically in the xps_true_callback_glyph_name function located in xps/xpsttf.c. This flaw represents a classic buffer over-read condition that occurs when processing specially crafted XPS (XML Paper Specification) files, making it a significant concern for systems that handle document processing and rendering. The vulnerability is classified under CWE-125 as an out-of-bounds read, which is a well-documented weakness in software development that can lead to system instability and potential exploitation.
The technical implementation of this vulnerability involves the improper handling of glyph name callbacks during the processing of TrueType font data within XPS documents. When a maliciously crafted XPS file is processed, the xps_true_callback_glyph_name function fails to properly validate input parameters, particularly the glyph name data structure, leading to memory access violations. The function attempts to read beyond the allocated memory boundaries when processing the glyph names, resulting in segmentation faults that cause the application to crash. This behavior aligns with the ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage application vulnerabilities to disrupt service availability.
From an operational perspective, this vulnerability presents a substantial risk to organizations that rely on Ghostscript for document processing, particularly in environments where untrusted documents are processed automatically. The denial of service impact can be severe in high-availability systems where continuous operation is critical, potentially leading to service interruptions that affect business operations. Attackers can exploit this vulnerability by simply preparing a malicious XPS file and presenting it to a system running the vulnerable Ghostscript version, making it a low-barrier attack vector. The vulnerability is particularly concerning in web applications or document processing pipelines where users might upload or receive XPS documents from untrusted sources.
The mitigation strategies for CVE-2017-9619 primarily involve upgrading to a patched version of Ghostscript where the input validation has been strengthened. Organizations should implement comprehensive patch management processes to ensure all systems running Ghostscript are updated promptly. Additionally, deploying input validation measures at the application level, such as implementing strict file format validation and sandboxing document processing components, can provide additional defense-in-depth. Network segmentation and access controls can limit the potential impact if an attacker successfully exploits this vulnerability. The vulnerability also underscores the importance of proper software security testing, particularly for font rendering and document processing libraries, as it demonstrates how seemingly benign input processing can lead to critical system instability. This issue exemplifies the broader challenge of securing complex document processing systems where multiple font formats and rendering engines interact, highlighting the need for robust memory safety practices and comprehensive testing of edge cases in document handling software.