CVE-2018-15909 in Ghostscript
Summary
by MITRE
In Artifex Ghostscript 9.23 before 2018-08-24, a type confusion using the .shfill operator could be used by attackers able to supply crafted PostScript files to crash the interpreter or potentially execute code.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-15909 represents a critical type confusion flaw within Artifex Ghostscript version 9.23 and earlier, which was addressed in the subsequent release on 2018-08-24. This issue specifically manifests through the exploitation of the .shfill operator, a PostScript command designed for rendering shaded fills in graphical output. The vulnerability arises from improper handling of data types during the interpretation of maliciously crafted PostScript files, creating conditions where the interpreter incorrectly processes memory structures, leading to unpredictable behavior.
The technical root cause of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which covers buffer overflow vulnerabilities in heap-based memory. The flaw occurs when Ghostscript processes PostScript code containing malicious .shfill operator usage, where the interpreter fails to properly validate type information associated with the data structures being manipulated. This type confusion allows attackers to manipulate memory layout in ways that can trigger arbitrary code execution or system crashes. The vulnerability is particularly dangerous because it can be exploited through PostScript files that might be encountered during normal document processing operations, making it a significant threat vector for both targeted attacks and broader exploitation campaigns.
From an operational perspective, this vulnerability creates substantial risk for organizations relying on Ghostscript for document processing, particularly in environments where untrusted PostScript files might be processed. The potential for remote code execution means that attackers could leverage this flaw to gain unauthorized access to systems, execute malicious payloads, or establish persistent backdoors. The attack surface extends to any application or service that utilizes Ghostscript for rendering PostScript or PDF documents, including web applications, document management systems, and print servers. The vulnerability's exploitation requires minimal privileges since it operates within the context of the Ghostscript interpreter itself, making it particularly attractive to threat actors seeking to compromise systems through document-based attacks.
Security mitigations for CVE-2018-15909 primarily focus on immediate remediation through software updates to Ghostscript versions released after 2018-08-24, which contain the necessary patches addressing the type confusion issue. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing Ghostscript are updated promptly. Additional protective measures include implementing strict input validation for all PostScript and PDF files processed by systems, deploying sandboxing mechanisms to isolate document processing operations, and establishing network segmentation to limit potential lateral movement if exploitation occurs. The vulnerability also highlights the importance of adhering to secure coding practices and conducting regular security assessments of interpreter-based software components, particularly those handling untrusted input data streams. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command and control communications and privilege escalation, as exploitation could potentially enable attackers to establish persistent access to compromised systems through the execution of malicious code within the Ghostscript processing environment.