CVE-2018-17183 in Ghostscript
Summary
by MITRE
Artifex Ghostscript before 9.25 allowed a user-writable error exception table, which could be used by remote attackers able to supply crafted PostScript to potentially overwrite or replace error handlers to inject code.
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Analysis
by VulDB Data Team • 05/17/2023
CVE-2018-17183 represents a critical vulnerability in Artifex Ghostscript versions prior to 9.25 that stems from improper handling of error exception tables during PostScript processing. This vulnerability falls under the category of memory corruption flaws and is classified as CWE-122, which deals with insufficient synchronization of data structures. The flaw occurs when Ghostscript processes crafted PostScript input that manipulates the error exception table, a critical component responsible for handling runtime errors during document rendering. The vulnerability arises because the error exception table is stored in a user-writable memory region, allowing attackers to modify its contents during processing.
The technical exploitation of this vulnerability requires an attacker to supply malicious PostScript code that can manipulate the error handling mechanism. When Ghostscript encounters an error during processing, it consults the error exception table to determine how to handle the situation. By carefully crafting PostScript code that modifies the exception table contents, an attacker can redirect error handling to execute arbitrary code. This represents a sophisticated attack vector that leverages the interpreter's error handling architecture to achieve code execution. The vulnerability is particularly concerning because it can be exploited remotely through untrusted PostScript input, making it applicable in web-based document processing scenarios.
The operational impact of CVE-2018-17183 extends beyond simple code execution, as it can enable attackers to achieve arbitrary code execution within the context of the Ghostscript process. This allows for privilege escalation, data exfiltration, and potential system compromise. The vulnerability affects various deployment scenarios including web applications, document processing servers, and any system that processes PostScript documents through Ghostscript. Attackers can leverage this flaw to bypass security controls, as the error handling mechanism is typically not subject to the same security restrictions as regular code paths. The attack surface is particularly broad given Ghostscript's widespread use in enterprise environments for document rendering and conversion.
Mitigation strategies for CVE-2018-17183 focus on immediate patching to version 9.25 or later, which addresses the underlying issue by properly securing the error exception table memory regions. Organizations should implement strict input validation and sanitization for all PostScript content, particularly in web-facing applications. Network segmentation and access controls can limit the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual error handling patterns and memory access violations during document processing. The vulnerability aligns with ATT&CK technique T1059.007 for script-based execution and T1068 for local privilege escalation. Additionally, implementing sandboxing mechanisms and restricting file system access for Ghostscript processes can provide defense-in-depth measures against exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify systems running vulnerable versions of Ghostscript.