CVE-2017-9611 in Ghostscript GhostXPS
Summary
by MITRE
The Ins_MIRP function in base/ttinterp.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-2017-9611 resides within the Ins_MIRP function located in the base/ttinterp.c file of Artifex Ghostscript GhostXPS version 9.22. 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 vulnerability specifically affects the TrueType interpreter component of the software, which is responsible for processing font instructions and rendering text elements within document processing workflows. The issue manifests when the interpreter attempts to process malformed or specially constructed TrueType font data, leading to memory access violations that can result in application instability.
The technical implementation of this vulnerability involves the Ins_MIRP function which handles the MIRP (Move Indirect Relative Point) instruction within TrueType font programs. When processing malicious input, the function fails to properly validate array bounds before accessing heap memory locations, resulting in a buffer over-read condition. This occurs because the interpreter does not adequately check the indices used to access font data structures, allowing an attacker to manipulate memory access patterns through carefully crafted font instructions. The vulnerability is classified under CWE-125 as an "Out-of-bounds Read" which is a common category of memory safety issues in interpreted environments. The flaw enables attackers to cause heap corruption that manifests as application crashes, potentially leading to denial of service conditions where legitimate users cannot access the system or process documents.
The operational impact of CVE-2017-9611 extends beyond simple denial of service scenarios, as it can potentially enable more sophisticated attacks depending on the execution environment. When an application crashes due to this vulnerability, it creates opportunities for attackers to disrupt business operations and potentially gain unauthorized access to systems processing documents. The vulnerability is particularly concerning in enterprise environments where Ghostscript is used for document conversion, rendering, and processing services. From an adversary perspective, this vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1070.004 for "Indicator Removal on Host: File Deletion" as attackers can leverage the instability to create persistent access points or to execute additional malicious payloads. The vulnerability affects systems where Ghostscript is integrated into document processing pipelines, including web applications, document management systems, and print servers that handle user-uploaded content.
Mitigation strategies for CVE-2017-9611 should include immediate patching of affected Ghostscript installations to version 9.23 or later, which contains the necessary fixes for the buffer over-read condition. Organizations should also implement document validation and sanitization processes that filter out potentially malicious font data before processing documents through Ghostscript. Network-based defenses such as web application firewalls and content filtering systems can help detect and block malicious documents before they reach vulnerable systems. Additionally, implementing proper input validation and bounds checking within applications that utilize Ghostscript as a library component can provide additional layers of protection. The vulnerability highlights the importance of maintaining up-to-date software components and implementing robust security practices in document processing environments, particularly in systems that handle untrusted user input. Regular security assessments and vulnerability scanning should include checks for outdated Ghostscript installations to prevent exploitation of this and similar memory safety vulnerabilities.