CVE-2018-16540 in Ghostscript
Summary
by MITRE
In Artifex Ghostscript before 9.24, attackers able to supply crafted PostScript files to the builtin PDF14 converter could use a use-after-free in copydevice handling to crash the interpreter or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability CVE-2018-16540 represents a critical use-after-free condition within the Artifex Ghostscript software suite, specifically affecting versions prior to 9.24. This flaw exists within the builtin PDF14 converter functionality that processes PostScript files, creating a dangerous attack surface where malicious actors can manipulate the interpreter through crafted input. The vulnerability stems from improper memory management during copydevice operations, where freed memory locations are accessed after the original memory allocation has been released, leading to unpredictable behavior.
The technical implementation of this vulnerability occurs when the Ghostscript interpreter processes specially crafted PostScript files that trigger the PDF14 converter's copydevice handling mechanism. During this process, the software allocates memory for device objects and subsequently frees them when the operation completes. However, the flawed implementation fails to properly invalidate references to these freed memory locations, allowing an attacker to manipulate the interpreter into accessing already-released memory segments. This memory corruption can manifest as immediate interpreter crashes or potentially enable more sophisticated exploitation techniques depending on the execution environment and memory layout.
From an operational impact perspective, this vulnerability poses significant risks to organizations relying on Ghostscript for document processing and conversion tasks. The ability to cause interpreter crashes represents a denial-of-service threat that can disrupt critical document workflows and rendering services. Additionally, the unspecified other impacts mentioned in the vulnerability description suggest potential for remote code execution or privilege escalation scenarios, particularly when Ghostscript is deployed in server environments or used for processing untrusted input from external sources. The vulnerability affects both the stability and security posture of systems that depend on Ghostscript's PDF conversion capabilities.
Organizations should prioritize immediate patching to version 9.24 or later, as this release contains the necessary memory management fixes to prevent the use-after-free condition. System administrators should also implement input validation controls to filter potentially malicious PostScript files before processing, particularly when Ghostscript is used in multi-user or internet-facing environments. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and could potentially map to ATT&CK technique T1059.007 for remote code execution through interpreter manipulation. Security monitoring should focus on detecting unusual interpreter crashes or memory access patterns that might indicate exploitation attempts, while network segmentation and access controls should limit exposure of Ghostscript services to untrusted users.