CVE-2017-8908 in Ghostscript
Summary
by MITRE
The mark_line_tr function in gxscanc.c in Artifex Ghostscript 9.21 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted PostScript document.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-8908 resides within the Ghostscript document processing library, specifically in the mark_line_tr function located in the gxscanc.c source file. This flaw represents a classic out-of-bounds read condition that occurs when processing maliciously crafted PostScript documents, making it a significant security concern for any system that processes PostScript content. The vulnerability affects Ghostscript version 9.21 and potentially earlier versions, demonstrating how seemingly minor flaws in document parsing can create substantial operational risks. Such vulnerabilities are particularly dangerous in environments where users might encounter untrusted document content, as they can be exploited to disrupt service availability without requiring elevated privileges.
The technical exploitation of this vulnerability occurs through careful manipulation of PostScript commands that trigger the mark_line_tr function during the scanning process of document rendering. When a malicious PostScript document is processed, the function fails to properly validate input boundaries, allowing an attacker to read memory locations beyond the intended data structures. This out-of-bounds memory access can result in unpredictable behavior including application crashes, which translates directly into a denial of service condition. The vulnerability operates at the level of document interpretation and rendering, making it particularly insidious as it can be triggered simply by opening or processing a malicious file, without requiring any special user interaction beyond the initial document load.
From an operational perspective, this vulnerability creates substantial risk for organizations relying on Ghostscript for document processing, printing, or conversion services. The denial of service impact means that legitimate users may be unable to process documents, leading to productivity losses and potential business disruption. Systems that automatically process incoming documents, such as email servers, print queues, or document management systems, become particularly vulnerable to this attack vector. The vulnerability can be exploited remotely through web-based interfaces or file sharing systems where PostScript documents are processed, making it a critical concern for any organization that handles untrusted document content. Network-based exploitation is possible when the vulnerable system processes documents from external sources, potentially allowing attackers to systematically disrupt services across multiple targets.
Security professionals should implement immediate mitigations including updating to Ghostscript versions that contain the patched mark_line_tr function, typically versions 9.22 or later. Organizations should also consider implementing document validation and sanitization measures that can detect and prevent malicious PostScript constructs from reaching the vulnerable parsing functions. Network segmentation and access controls can help limit the impact of potential exploitation attempts. The vulnerability aligns with CWE-125 out-of-bounds read classification and represents a potential entry point for broader attack chains that could leverage this denial of service condition to facilitate more sophisticated exploits. This type of vulnerability demonstrates the importance of thorough input validation and boundary checking in document processing systems, as specified in various security frameworks including those related to the ATT&CK framework's defense evasion and execution techniques. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other document processing libraries and applications that may be similarly affected by out-of-bounds memory access flaws.