CVE-2018-15908 in Ghostscript
Summary
by MITRE
In Artifex Ghostscript 9.23 before 2018-08-23, attackers are able to supply malicious PostScript files to bypass .tempfile restrictions and write files.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability CVE-2018-15908 represents a critical file system access control flaw in Artifex Ghostscript version 9.23 and earlier, which was addressed in the August 23, 2018 security update. This issue stems from inadequate validation of temporary file handling mechanisms within the PostScript interpreter, creating a path for malicious actors to circumvent intended security restrictions. The vulnerability specifically targets the .tempfile directive functionality that is designed to control where temporary files are created and how they are managed during PostScript processing operations.
The technical exploitation of this vulnerability occurs through carefully crafted PostScript files that manipulate the temporary file creation process. Attackers can construct malicious input that bypasses the intended restrictions on temporary file locations and permissions, effectively allowing arbitrary file write operations to occur in directories where such access would normally be prohibited. This flaw operates at the core of Ghostscript's file system interaction layer, where the software's handling of temporary file names and locations fails to properly validate or sanitize user-supplied input. The vulnerability manifests as a path traversal or privilege escalation issue within the sandboxing mechanisms that are supposed to isolate file system operations during PostScript interpretation.
The operational impact of CVE-2018-15908 is substantial as it enables attackers to write files to arbitrary locations on the target system, potentially leading to persistent malware installation, credential theft, or further system compromise. This vulnerability can be particularly dangerous in environments where Ghostscript is used to process untrusted documents, such as email attachments, document conversion services, or web applications that utilize Ghostscript for PDF rendering. The ability to bypass .tempfile restrictions means that attackers can potentially write malicious executables, configuration files, or data exfiltration tools directly to the file system without proper authorization. The vulnerability affects both local and remote exploitation scenarios, making it a significant concern for organizations running vulnerable versions of Ghostscript in production environments.
Security mitigations for CVE-2018-15908 primarily involve upgrading to Ghostscript version 9.23 or later, which includes the necessary patches to address the temporary file handling vulnerability. Organizations should also implement additional defensive measures such as restricting file system access for Ghostscript processes, implementing strict input validation for all PostScript files, and monitoring for unauthorized file creation events. The vulnerability aligns with CWE-22 Path Traversal and CWE-73 Path Traversal in the Common Weakness Enumeration catalog, while also mapping to ATT&CK techniques involving privilege escalation and persistence through file system manipulation. System administrators should conduct thorough vulnerability assessments to identify systems running vulnerable versions of Ghostscript and ensure proper patch management procedures are in place to prevent exploitation of this and similar file system access control vulnerabilities.