CVE-2023-52722: Artifex Ghostscript Security Vulnerability

CVE-2023-52722 Overview

CVE-2023-52722 is an authorization bypass vulnerability discovered in Artifex Ghostscript before version 10.03.1. The vulnerability exists in the psi/zmisc1.c component, where SAFER mode fails to properly restrict eexec seeds to the Type 1 standard. This flaw allows attackers to use non-standard eexec seeds when SAFER mode is enabled, potentially bypassing security restrictions designed to limit Ghostscript's capabilities when processing untrusted documents.

Critical Impact

Attackers can bypass SAFER mode security restrictions in Ghostscript by leveraging non-standard eexec seeds, potentially enabling unauthorized file system modifications when processing malicious PostScript or PDF files.

Affected Products

• Artifex Ghostscript versions prior to 10.03.1
• Systems using Ghostscript for PDF/PostScript processing with SAFER mode enabled
• Applications and services that rely on Ghostscript's SAFER mode for security isolation

Discovery Timeline

• 2024-04-28 - CVE-2023-52722 published to NVD
• 2025-06-23 - Last updated in NVD database

Technical Details for CVE-2023-52722

Vulnerability Analysis

This vulnerability represents an authorization bypass in Ghostscript's SAFER mode implementation. SAFER mode is a critical security feature designed to restrict Ghostscript's access to the file system and prevent execution of potentially dangerous operations when processing untrusted documents. The vulnerability in psi/zmisc1.c allows the use of eexec seeds that deviate from the Type 1 font standard, which can be leveraged to circumvent these security restrictions.

The eexec encoding mechanism is a legacy obfuscation technique used in PostScript Type 1 fonts. When SAFER mode is active, Ghostscript should only accept the standard eexec seed value (55665) to maintain security boundaries. However, the vulnerable code path allows alternative seed values, creating an avenue for attackers to craft malicious documents that can perform unauthorized operations.

Root Cause

The root cause lies in insufficient validation within the psi/zmisc1.c file. When Ghostscript processes eexec-encoded content in SAFER mode, the code fails to enforce that only the standard Type 1 eexec seed (55665) is accepted. This oversight allows attackers to supply arbitrary seed values, which can be used to decode malicious PostScript code that bypasses SAFER mode restrictions. The fix involves adding proper validation to ensure that only the standard seed is accepted when operating in SAFER mode.

Attack Vector

The attack requires local access with user interaction, typically through processing a maliciously crafted PostScript or PDF document. An attacker would craft a document containing eexec-encoded content with a non-standard seed value. When a user or automated system processes this document using Ghostscript with SAFER mode enabled, the malicious code bypasses security restrictions that would normally prevent file system modifications or other dangerous operations.

The attack scenario typically involves:

1. An attacker creates a malicious PostScript or PDF file containing eexec-encoded content with a non-standard seed
2. The victim opens or processes the file using Ghostscript (directly or through an application that uses Ghostscript)
3. Despite SAFER mode being enabled, the non-standard seed allows the embedded code to execute with elevated capabilities
4. The attacker achieves unauthorized file system write access or other restricted operations

For technical details regarding the vulnerability mechanism and the specific code changes, refer to the Ghostscript Commit Update.

Detection Methods for CVE-2023-52722

Indicators of Compromise

• PostScript or PDF files containing eexec sections with non-standard seed values (anything other than 55665)
• Unexpected file system modifications occurring during document processing operations
• Ghostscript processes attempting to access files or directories outside expected working paths

Detection Strategies

• Monitor Ghostscript process activity for file system write operations when processing untrusted documents
• Implement file integrity monitoring on systems that process untrusted PDF/PostScript content
• Deploy endpoint detection rules that flag Ghostscript child processes or unexpected file access patterns
• Audit document processing workflows for anomalous behavior patterns

Monitoring Recommendations

• Enable verbose logging for Ghostscript operations in production environments
• Implement sandbox monitoring for document conversion services
• Configure SentinelOne Singularity to monitor Ghostscript process behavior and file system activity
• Review logs for Ghostscript invocations processing documents from untrusted sources

How to Mitigate CVE-2023-52722

Immediate Actions Required

• Upgrade Artifex Ghostscript to version 10.03.1 or later immediately
• Audit systems for vulnerable Ghostscript installations using package managers or version queries
• Implement additional sandboxing for document processing workflows until patching is complete
• Review and restrict access to Ghostscript on multi-user systems

Patch Information

Artifex has released a security fix in Ghostscript version 10.03.1. The patch modifies psi/zmisc1.c to properly enforce Type 1 standard eexec seed validation when SAFER mode is active. The fix is available in commit afd7188f74918cb51b5fb89f52b54eb16e8acfd1. Organizations should update to version 10.03.1 or apply the specific commit to their installations. See the Ghostscript Commit Update for patch details.

Workarounds

• Run Ghostscript in a containerized or sandboxed environment with restricted file system access
• Disable Ghostscript processing of untrusted documents until the patch can be applied
• Implement strict input validation to reject documents before Ghostscript processing where possible
• Use application-level firewall rules to restrict Ghostscript's network and file system capabilities

# Check installed Ghostscript version
gs --version

# Example: Running Ghostscript in a restricted container
docker run --rm -v /input:/input:ro -v /output:/output ghostscript:10.03.1 -sDEVICE=pdfwrite -dSAFER -o /output/out.pdf /input/document.pdf