CVE-2018-19477 in Ghostscript
Summary
by MITRE
psi/zfjbig2.c in Artifex Ghostscript before 9.26 allows remote attackers to bypass intended access restrictions because of a JBIG2Decode type confusion.
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Analysis
by VulDB Data Team • 06/11/2023
CVE-2018-19477 represents a critical type confusion vulnerability within the JBIG2Decode implementation of Artifex Ghostscript version 9.26 and earlier. This flaw exists in the psi/zfjbig2.c file where the software fails to properly validate data types during the processing of JBIG2 compressed image data. The vulnerability stems from inadequate input validation mechanisms that allow maliciously crafted JBIG2 files to manipulate the type system, leading to potential arbitrary code execution or bypass of access controls. The issue manifests when the software processes JBIG2 encoded images without sufficient type checking, enabling attackers to manipulate memory layouts and execute unauthorized operations.
The technical exploitation of this vulnerability leverages fundamental principles of type confusion attacks where the program incorrectly handles data types during processing operations. When Ghostscript encounters a specially crafted JBIG2 file, the lack of proper type validation allows attackers to manipulate the program's internal state by forcing the software to treat one data type as another. This type confusion can result in memory corruption that adversaries can potentially leverage for privilege escalation or remote code execution. The vulnerability specifically affects the JBIG2Decode filter implementation which is used to decompress JBIG2 compressed images, making it particularly dangerous in environments where PDF processing is common.
The operational impact of CVE-2018-19477 extends beyond simple access bypass to encompass potential system compromise across various deployment scenarios. Organizations utilizing Ghostscript for PDF rendering, document processing, or print server operations face significant risk when exposed to malicious JBIG2 content. This vulnerability is particularly concerning in web applications, email servers, and document management systems that process untrusted PDF files containing JBIG2 encoded images. The remote exploitation capability means that attackers can trigger the vulnerability through web-based PDF viewers or document processing services without requiring local access to the target system. The attack surface is further expanded due to Ghostscript's widespread use in enterprise environments, making this vulnerability a high-priority concern for security teams.
Mitigation strategies for CVE-2018-19477 should focus on immediate patch deployment and implementation of additional protective measures. The primary recommendation involves upgrading to Ghostscript version 9.26 or later where the type confusion vulnerability has been addressed through proper input validation and type checking mechanisms. Organizations should also implement network-level filtering to restrict access to JBIG2 content when possible, particularly in environments where PDF processing occurs. Additionally, deploying intrusion detection systems that can identify suspicious JBIG2 file patterns and implementing sandboxing techniques for PDF processing can provide additional layers of protection. The vulnerability aligns with CWE-129, which describes improper validation of array indices, and can be mapped to ATT&CK technique T1203 for legitimate program execution with elevated privileges, emphasizing the need for comprehensive security controls beyond simple patching.