CVE-2018-16541 in Ghostscript
Summary
by MITRE
In Artifex Ghostscript before 9.24, attackers able to supply crafted PostScript files could use incorrect free logic in pagedevice replacement to crash the interpreter.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16541 affects Artifex Ghostscript versions prior to 9.24 and represents a critical memory corruption issue stemming from improper handling of pagedevice replacement logic within the PostScript interpreter. This flaw resides in the core processing mechanisms that manage how graphical output devices are handled during document rendering, creating a pathway for remote code execution or denial of service through carefully crafted malicious PostScript files. The vulnerability specifically targets the interpreter's memory management subsystem where it fails to properly validate or handle the replacement of pagedevice objects during document processing, leading to potential heap corruption and system instability.
The technical implementation of this vulnerability involves a flaw in the free logic mechanism that governs how memory allocated for pagedevice objects is released and reused. When Ghostscript processes PostScript files containing maliciously constructed pagedevice replacement sequences, the interpreter's memory management routines fail to properly validate the object references, resulting in double-free conditions or use-after-free scenarios. This occurs because the pagedevice replacement code path does not adequately verify the integrity of the replacement objects or properly handle the transition between different device contexts. The vulnerability manifests when the interpreter attempts to free memory associated with pagedevice objects that have already been freed or are in an inconsistent state, causing the interpreter to crash or behave unpredictably.
From an operational perspective, this vulnerability presents significant risk to organizations that process untrusted PostScript or PDF documents, particularly in environments where document conversion, printing, or rendering services are exposed to external users. Attackers could exploit this vulnerability by crafting malicious PostScript files designed to trigger the specific memory corruption scenario during document processing, potentially leading to system crashes, application instability, or in more severe cases, arbitrary code execution. The impact extends beyond simple denial of service as the memory corruption could be leveraged to bypass security controls or escalate privileges within the processing environment. Organizations relying on Ghostscript for document handling, including web applications, print servers, and document conversion services, face potential exposure to this vulnerability.
The remediation strategy centers on upgrading to Ghostscript version 9.24 or later, which includes fixed implementations of the pagedevice replacement logic that properly validate object references and handle memory deallocation sequences. Security administrators should prioritize patching affected systems and implementing proper input validation for all PostScript and PDF processing workflows. Additional mitigations include deploying sandboxing mechanisms around document processing services, implementing strict file format validation, and monitoring for unusual memory allocation patterns or crash events in processing environments. This vulnerability aligns with CWE-415 which addresses double free conditions in memory management, and could be categorized under ATT&CK technique T1059 for execution through interpreted languages, particularly in the context of document processing services. Organizations should also consider implementing network segmentation and access controls to limit exposure of vulnerable services to untrusted users.