CVE-2018-19476 in Ghostscript
Summary
by MITRE
psi/zicc.c in Artifex Ghostscript before 9.26 allows remote attackers to bypass intended access restrictions because of a setcolorspace type confusion.
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Analysis
by VulDB Data Team • 06/11/2023
The vulnerability identified as CVE-2018-19476 represents a critical type confusion flaw within the Ghostscript rendering engine developed by Artifex. This issue specifically affects the psi/zicc.c component which handles color space processing during document rendering operations. The vulnerability arises from improper type validation during color space manipulation, creating a scenario where maliciously crafted input can manipulate the interpreter's internal state to bypass intended access controls. Such type confusion vulnerabilities are particularly dangerous because they can lead to arbitrary code execution or information disclosure when the interpreter incorrectly handles data types during processing operations. The flaw exists in Ghostscript versions prior to 9.26, making it a significant concern for organizations running older versions of this widely used PostScript and PDF interpreter.
The technical implementation of this vulnerability stems from a fundamental flaw in how Ghostscript processes color space operations within the zicc.c module. When processing color space definitions, the system fails to properly validate type consistency between expected and actual data structures. This type confusion allows attackers to manipulate the interpreter's internal state by providing carefully crafted color space parameters that cause the system to treat one data type as another. The vulnerability specifically affects the setcolorspace operation which is commonly used in PostScript and PDF documents to define color rendering contexts. According to CWE-466, this represents a classic type confusion issue where the program's type system is violated, leading to unpredictable behavior that can be exploited for malicious purposes. The flaw demonstrates poor input validation practices and highlights the importance of robust type checking in interpreted languages and graphics processing systems.
The operational impact of CVE-2018-19476 extends beyond simple privilege escalation to encompass potential remote code execution and information disclosure capabilities. Attackers can leverage this vulnerability to bypass access restrictions that are typically enforced during document processing, potentially gaining unauthorized access to systems that process untrusted documents. This is particularly concerning in environments where Ghostscript is used for document conversion, printing, or PDF processing services, as these systems often handle documents from untrusted sources. The vulnerability aligns with ATT&CK technique T1203 by enabling attackers to bypass security controls through manipulation of system internals. Organizations running vulnerable versions of Ghostscript face significant risk when processing documents from external sources, as the attack surface includes web applications, document management systems, and print servers that rely on Ghostscript for rendering operations. The remote nature of the attack means that exploitation can occur without requiring local system access, making it particularly dangerous for network-facing services.
Mitigation strategies for CVE-2018-19476 primarily focus on immediate version updates to Ghostscript 9.26 or later, which contain the necessary patches to address the type confusion vulnerability. System administrators should prioritize patching across all environments where Ghostscript is deployed, particularly in web applications, document processing systems, and print servers. Additional defensive measures include implementing strict input validation for document processing pipelines, using sandboxing techniques to limit the impact of potential exploitation, and monitoring for suspicious document processing activities. Organizations should also consider implementing network segmentation to limit access to systems running Ghostscript, particularly those handling untrusted input. The vulnerability demonstrates the importance of regular security updates and proper input validation in interpreted environments, aligning with security best practices outlined in NIST SP 800-128 and ISO/IEC 27001 controls. Organizations should conduct vulnerability assessments to identify all systems running affected Ghostscript versions and establish monitoring procedures to detect potential exploitation attempts.