CVE-2020-17538 in Ghostscript
Summary
by MITRE
A buffer overflow vulnerability in GetNumSameData() in contrib/lips4/gdevlips.c of Artifex Software GhostScript v9.50 allows a remote attacker to cause a denial of service via a crafted PDF file. This is fixed in v9.51.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2020-17538 represents a critical buffer overflow flaw within the GhostScript PDF processing engine developed by Artifex Software. This issue specifically affects version 9.50 of the software and resides within the GetNumSameData() function located in the contrib/lips4/gdevlips.c source file. The flaw manifests during the processing of PostScript and PDF documents, where the software fails to properly validate input data length before attempting to copy or process it into fixed-size buffers. This particular code module handles device-independent graphics processing for laser printers and similar output devices, making it a critical component in the document rendering pipeline. The vulnerability's location within the graphics device driver layer indicates that it operates at a level where it can directly influence how visual elements are rendered and processed, creating a potential attack surface that extends beyond simple text processing.
The technical exploitation of this buffer overflow occurs when a maliciously crafted PDF file contains specially constructed data that triggers the GetNumSameData() function with input exceeding the allocated buffer boundaries. This condition allows an attacker to overwrite adjacent memory locations, potentially leading to arbitrary code execution or system instability. The flaw is classified under CWE-121 as a stack-based buffer overflow, where insufficient bounds checking permits memory corruption during data processing operations. The vulnerability's remote exploitability means that an attacker can deliver the malicious payload through web browsers, email attachments, or any system that processes PDF documents using the affected GhostScript version. This characteristic significantly broadens the attack surface and makes the vulnerability particularly dangerous in enterprise environments where PDF processing is common.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially enable more sophisticated attacks that compromise system integrity and availability. When exploited successfully, the buffer overflow can cause the GhostScript process to crash or behave unpredictably, leading to service disruption for legitimate users. In environments where GhostScript is used for document conversion, printing services, or web applications that process user-uploaded PDF files, this vulnerability can result in significant operational downtime and potential data loss. The attack vector through crafted PDF files means that even seemingly benign document processing can become a security risk, particularly in organizations that do not maintain strict content filtering policies for PDF documents. The vulnerability affects systems that rely on GhostScript for rendering PDF content, including web servers, print management systems, and document processing applications that integrate the software as a backend component.
Mitigation strategies for CVE-2020-17538 primarily involve upgrading to GhostScript version 9.51 or later, which contains the necessary patches to address the buffer overflow condition. System administrators should prioritize patch management to ensure all instances of GhostScript within their environment are updated to the latest secure version. Additional protective measures include implementing strict input validation for PDF documents, deploying sandboxed environments for document processing, and configuring web applications to sanitize or validate PDF content before processing. Network-based mitigations such as implementing web application firewalls and content filtering systems can help prevent exploitation attempts by blocking suspicious PDF content. The vulnerability's classification under the ATT&CK framework as a privilege escalation or code execution technique highlights the need for comprehensive security monitoring and incident response procedures. Organizations should also consider implementing runtime protection mechanisms that can detect and prevent buffer overflow exploitation attempts, particularly in high-risk environments where PDF processing occurs frequently. Regular security assessments and vulnerability scanning should include verification of GhostScript installations to ensure no instances remain vulnerable to this specific buffer overflow condition.