Artifex Ghostscript 10.2.1 DoS

Overview

Artifex Ghostscript is an interpreter for PostScript and PDF files. Versions prior to 10.2.1 contain multiple vulnerabilities that can lead to Denial of Service (DoS) attacks, allowing attackers to crash the application or exhaust system resources.

• Severity: Medium

Impact

• Application Crash: Vulnerabilities can be exploited to crash Ghostscript, rendering it unusable.
• Resource Exhaustion: Attackers can cause the application to consume excessive system resources, leading to performance degradation and potential system outages.
• Service Disruption: Continuous exploitation can result in prolonged service downtime, affecting availability.

Cause

• Memory Handling Errors: Improper memory allocation and deallocation can lead to crashes.
• Infinite Loop Bugs: Certain crafted inputs can cause the application to enter infinite loops, consuming CPU and memory resources.
• Improper Input Validation: Failure to properly validate inputs can allow malicious files to exploit vulnerabilities in Ghostscript.

Solution

1. Update to Latest Version:

   • Ensure Ghostscript is updated to version 10.2.1 or later, which includes fixes for known DoS vulnerabilities.

     sudo apt-get update
     sudo apt-get install ghostscript

2. Implement Input Validation

   • Validate and sanitize all inputs before processing them with Ghostscript to mitigate the risk of malicious files.

3. Limit Resource Usage:

   • Configure resource limits for Ghostscript processes to prevent resource exhaustion attacks.

     ulimit -v 1048576  # Set a limit of 1GB of virtual memory

Examples

Practical Example

# Example exploit to trigger a DoS condition in Ghostscript
gs -q -dSAFER -dNODISPLAY -c "300000000 300000000 scale 0 0 moveto 1 setlinewidth stroke"

This example shows how a crafted PostScript command can be used to exploit a vulnerability in Ghostscript, causing it to consume excessive resources and potentially crash.

Updating Ghostscript

1. For Ubuntu/Debian:

   sudo apt-get update
   sudo apt-get install ghostscript

2. For Red Hat/CentOS:

   sudo yum update
   sudo yum install ghostscript

References

• Ghostscript Overview
• BSI - Concept Exploit in Ghostscript

Additional Resources

• How to build Ghostscript from source code