CVE-2024-46952: Artifex Ghostscript Buffer Overflow Flaw

CVE-2024-46952 Overview

CVE-2024-46952 is a buffer overflow vulnerability discovered in Artifex Ghostscript, specifically within the pdf/pdf_xref.c file. The vulnerability occurs during the handling of PDF XRef streams, related to improper processing of W array values. Ghostscript is a widely deployed interpreter for PostScript and PDF files, commonly used in document processing pipelines, print servers, and various applications that render or convert PDF documents.

This buffer overflow vulnerability allows attackers to potentially corrupt memory by crafting malicious PDF files with specially constructed XRef stream data. When a vulnerable version of Ghostscript processes such a file, the improper handling of W array values can lead to memory corruption, potentially enabling arbitrary code execution with the privileges of the user running Ghostscript.

Critical Impact

Successful exploitation of this buffer overflow vulnerability could allow an attacker to execute arbitrary code on systems running vulnerable versions of Ghostscript, potentially leading to complete system compromise through maliciously crafted PDF documents.

Affected Products

• Artifex Ghostscript versions before 10.04.0
• Debian Linux 12.0 (with bundled Ghostscript packages)
• Any software or system utilizing vulnerable Ghostscript libraries for PDF processing

Discovery Timeline

• 2024-11-10 - CVE-2024-46952 published to NVD
• 2024-11-14 - Last updated in NVD database

Technical Details for CVE-2024-46952

Vulnerability Analysis

The vulnerability exists in the PDF XRef stream parsing functionality within pdf/pdf_xref.c. PDF XRef (cross-reference) streams are a compressed format for storing the cross-reference table in PDF files, which contains information about the location of objects within the document. The W array in a PDF XRef stream defines the byte widths of each field in the stream entries.

When Ghostscript processes a PDF file containing a malformed XRef stream with crafted W array values, insufficient bounds checking allows data to be written beyond the allocated buffer boundaries. This classic buffer overflow condition (CWE-120) can corrupt adjacent memory structures, potentially allowing an attacker to hijack program execution flow.

The local attack vector requires user interaction—typically a user opening or processing a malicious PDF file. Given Ghostscript's common use in automated document processing pipelines, this could also be triggered in server-side contexts where untrusted PDFs are processed.

Root Cause

The root cause of this vulnerability is insufficient bounds checking when processing W array values in PDF XRef streams. The code in pdf/pdf_xref.c failed to properly validate the size parameters specified in the W array before allocating and writing to buffers, allowing carefully crafted values to trigger a buffer overflow condition.

Attack Vector

Exploitation requires local access and user interaction. An attacker must craft a malicious PDF document containing a specially constructed XRef stream with manipulated W array values. The attack sequence typically involves:

1. Creating a PDF file with a malformed XRef stream containing oversized W array values
2. Delivering the malicious PDF to a target via email, file sharing, or web download
3. The victim opens or processes the PDF using Ghostscript or an application that relies on Ghostscript for PDF rendering
4. The buffer overflow is triggered during XRef stream parsing, potentially leading to code execution

The vulnerability is particularly concerning in environments where Ghostscript is used for automated PDF processing, such as print servers, document conversion services, or web applications that generate PDF previews.

Detection Methods for CVE-2024-46952

Indicators of Compromise

• Unexpected crashes or segmentation faults in Ghostscript processes when handling PDF files
• Core dumps or error logs indicating memory corruption in pdf_xref.c related functions
• Unusual process spawning from Ghostscript or gs binary execution contexts
• PDF files with anomalous XRef stream structures containing irregular W array values

Detection Strategies

• Deploy file integrity monitoring on Ghostscript binaries and libraries to detect unauthorized modifications
• Implement PDF file inspection at network perimeters to identify documents with malformed XRef streams
• Monitor for unusual Ghostscript process behavior including unexpected child process creation or network activity
• Use application sandboxing to isolate Ghostscript processes and detect breakout attempts

Monitoring Recommendations

• Configure logging for all Ghostscript invocations, including the source files being processed
• Enable crash reporting and analyze core dumps for signs of buffer overflow exploitation
• Monitor system call patterns from Ghostscript processes for anomalous behavior
• Implement network segmentation for systems running automated PDF processing workflows

How to Mitigate CVE-2024-46952

Immediate Actions Required

• Upgrade Artifex Ghostscript to version 10.04.0 or later immediately on all affected systems
• Audit all applications and services that depend on Ghostscript libraries for PDF processing
• Implement input validation to reject PDF files from untrusted sources until patching is complete
• Consider temporarily disabling automated PDF processing workflows that use vulnerable Ghostscript versions

Patch Information

Artifex has released a fix in Ghostscript version 10.04.0. The specific commit addressing this vulnerability is available in the Ghostscript Git Repository. Additional details can be found in the Ghostscript Bug Report #708001 and the Ghostscript News Document.

For Debian Linux 12.0 users, monitor the official Debian security advisories for updated packages containing the fix.

Workarounds

• Restrict PDF processing to trusted sources only and implement strict file validation
• Run Ghostscript in a sandboxed environment using tools like firejail, Docker containers, or AppArmor profiles
• Disable PDF XRef stream processing if possible through Ghostscript configuration options
• Implement network segmentation to isolate PDF processing systems from critical infrastructure

# Example: Running Ghostscript in a restricted sandbox with firejail
firejail --private --net=none --no3d gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf input.pdf

# Verify installed Ghostscript version
gs --version
# Ensure version is 10.04.0 or later