CVE-2023-46751: Artifex Ghostscript DOS Vulnerability

CVE-2023-46751 Overview

CVE-2023-46751 is a Use After Free vulnerability discovered in Artifex Ghostscript through version 10.02.0. The vulnerability exists in the gdev_prn_open_printer_seekable() function and allows remote attackers to crash the application via a dangling pointer. This memory corruption issue can lead to denial of service conditions when processing maliciously crafted documents.

Critical Impact

Remote attackers can cause application crashes through network-accessible attack vectors without requiring authentication or user interaction, potentially disrupting document processing workflows and print services.

Affected Products

• Artifex Ghostscript versions through 10.02.0
• Systems utilizing Ghostscript for PDF/PostScript processing
• Applications integrating Ghostscript libraries for document rendering

Discovery Timeline

• 2023-12-06 - CVE-2023-46751 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-46751

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption vulnerability that occurs when a program continues to reference memory after it has been freed. In the context of the gdev_prn_open_printer_seekable() function, the issue manifests as a dangling pointer that remains accessible after the memory it references has been deallocated.

The vulnerability can be triggered remotely over the network without requiring authentication or user interaction. When exploited, it results in a denial of service condition by crashing the Ghostscript application. While the confidentiality and integrity of the system are not directly impacted, the availability impact is significant as it can disrupt document processing operations.

Root Cause

The root cause of CVE-2023-46751 lies in improper memory management within the gdev_prn_open_printer_seekable() function. During the printer device initialization process, a pointer reference is maintained after the associated memory has been freed. This creates a dangling pointer scenario where subsequent operations attempt to access invalid memory locations, leading to undefined behavior and application crashes.

The specific code path involves the seekable printer device opening routine, where memory lifecycle management fails to properly track pointer validity states after deallocation events.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker can craft a malicious document (PDF, PostScript, or other Ghostscript-supported format) containing specific content that triggers the vulnerable code path during processing. When Ghostscript attempts to process this document, the dangling pointer is dereferenced, causing the application to crash.

The attack requires no privileges and no user interaction beyond the victim system processing the malicious document, which may occur automatically in print servers, document conversion services, or preview generation systems.

Detection Methods for CVE-2023-46751

Indicators of Compromise

• Unexpected Ghostscript process crashes or terminations during document processing
• Core dumps or crash logs referencing the gdev_prn_open_printer_seekable() function
• Abnormal system log entries indicating memory access violations in Ghostscript processes
• Repeated service restarts for applications depending on Ghostscript libraries

Detection Strategies

• Monitor Ghostscript processes for segmentation faults and abnormal termination signals
• Implement file integrity monitoring on Ghostscript configuration and binary files
• Deploy application-level monitoring to detect unusual crash patterns in document processing workflows
• Analyze incoming documents for suspicious characteristics before processing with Ghostscript

Monitoring Recommendations

• Configure crash reporting and analysis for Ghostscript-dependent services
• Establish baseline metrics for document processing success rates to detect anomalies
• Enable verbose logging for Ghostscript operations in production environments
• Set up alerts for repeated process crashes within short time windows

How to Mitigate CVE-2023-46751

Immediate Actions Required

• Update Artifex Ghostscript to a version beyond 10.02.0 that contains the security fix
• Review and restrict network access to systems running vulnerable Ghostscript versions
• Implement input validation and sandboxing for document processing workflows
• Consider temporarily disabling automated document processing until patches are applied

Patch Information

Artifex has released a fix for this vulnerability. The security patch addresses the dangling pointer issue in the gdev_prn_open_printer_seekable() function by implementing proper memory lifecycle management. The fix is tracked in the Ghostscript Git Repository with commit hash dcdbc595c13c9d11d235702dff46bb74c80f7698.

Debian users should reference Debian Security Advisory DSA-5578 for distribution-specific patching guidance. Additional details about the vulnerability can be found in Ghostscript Bug Report #707264.

Workarounds

• Isolate Ghostscript processing in sandboxed environments or containers with restricted permissions
• Implement network segmentation to limit exposure of systems running Ghostscript
• Use application firewalls to filter potentially malicious documents before they reach Ghostscript
• Configure resource limits and process monitoring to quickly detect and respond to crash events

# Configuration example - Sandboxing Ghostscript with resource limits
# Create a dedicated user for Ghostscript processing
useradd -r -s /bin/false ghostscript-worker

# Run Ghostscript with restricted permissions and resource limits
# Using systemd service configuration
cat << EOF > /etc/systemd/system/ghostscript-sandbox.service
[Service]
User=ghostscript-worker
MemoryLimit=512M
CPUQuota=50%
PrivateTmp=true
ProtectSystem=strict
NoNewPrivileges=true
EOF