CVE-2025-27834: Artifex Ghostscript Buffer Overflow Flaw

CVE-2025-27834 Overview

CVE-2025-27834 is a buffer overflow vulnerability discovered in Artifex Ghostscript before version 10.05.0. The vulnerability exists in the pdf/pdf_func.c component and can be triggered when processing a PDF document containing an oversized Type 4 function. This memory corruption flaw could allow an attacker to execute arbitrary code in the context of the application processing the malicious PDF file.

Critical Impact

Successful exploitation of this buffer overflow vulnerability could lead to arbitrary code execution, potentially allowing attackers to gain control of affected systems through maliciously crafted PDF documents.

Affected Products

• Artifex Ghostscript versions prior to 10.05.0

Discovery Timeline

• 2025-03-25 - CVE-2025-27834 published to NVD
• 2025-04-01 - Last updated in NVD database

Technical Details for CVE-2025-27834

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw occurs in the PDF function handling code within pdf/pdf_func.c when processing Type 4 functions in PDF documents.

Type 4 functions in PDF are PostScript calculator functions that can contain arbitrary PostScript expressions. When a maliciously crafted PDF document contains an oversized Type 4 function, the Ghostscript PDF interpreter fails to properly validate the size of the input data before copying it into a fixed-size buffer. This allows an attacker to overflow the buffer and potentially overwrite adjacent memory regions.

The vulnerability requires local access and user interaction, meaning the attacker must convince a user to open a malicious PDF file using an application that relies on Ghostscript for PDF rendering. Given Ghostscript's widespread use as a PDF processing backend in various applications, document management systems, and print services, the potential attack surface is significant.

Root Cause

The root cause of CVE-2025-27834 is improper bounds checking in the pdf/pdf_func.c source file when handling Type 4 PostScript calculator functions embedded in PDF documents. The code fails to validate that the size of the incoming Type 4 function data does not exceed the allocated buffer size, allowing memory corruption when oversized data is processed.

Attack Vector

The attack vector for this vulnerability is local, requiring user interaction. An attacker could exploit this vulnerability through the following scenario:

1. The attacker crafts a malicious PDF document containing an oversized Type 4 function designed to trigger the buffer overflow
2. The victim opens or processes the malicious PDF using an application that relies on Ghostscript for rendering
3. When Ghostscript processes the Type 4 function, the buffer overflow occurs
4. The attacker's payload overwrites memory, potentially achieving arbitrary code execution with the privileges of the user running the application

Common attack vectors include email attachments, malicious downloads, or exploitation through web applications that use Ghostscript for server-side PDF processing.

The vulnerability mechanism involves improper buffer size validation in the pdf/pdf_func.c component. When processing Type 4 PostScript calculator functions in PDF documents, the code copies function data into a buffer without adequately checking whether the input exceeds the buffer's allocated size. Technical details are available in the Ghostscript Bug Report #708253.

Detection Methods for CVE-2025-27834

Indicators of Compromise

• Unexpected Ghostscript crashes or segmentation faults when processing PDF files
• Anomalous memory consumption patterns during PDF rendering operations
• Suspicious PDF files with unusually large or complex Type 4 function definitions
• Application logs showing errors related to pdf/pdf_func.c or Type 4 function processing

Detection Strategies

• Monitor for Ghostscript process crashes, particularly when triggered by PDF file processing
• Implement file integrity monitoring on systems using Ghostscript to detect unauthorized modifications
• Deploy endpoint detection solutions capable of identifying buffer overflow exploitation attempts
• Analyze PDF files for anomalous Type 4 function sizes before processing

Monitoring Recommendations

• Enable detailed logging for applications utilizing Ghostscript PDF processing
• Configure security information and event management (SIEM) systems to alert on Ghostscript-related anomalies
• Monitor for unexpected child processes spawned by Ghostscript or applications using it
• Implement network monitoring for unusual outbound connections following PDF processing

How to Mitigate CVE-2025-27834

Immediate Actions Required

• Upgrade Artifex Ghostscript to version 10.05.0 or later immediately
• Audit systems to identify all instances of vulnerable Ghostscript installations
• Review applications and services that depend on Ghostscript for PDF processing
• Implement additional input validation for PDF files before processing with Ghostscript

Patch Information

Artifex has addressed this vulnerability in Ghostscript version 10.05.0. Organizations should upgrade to this version or later to remediate the vulnerability. Details about the fix are available in the Ghostscript Bug Report #708253.

Workarounds

• Disable or restrict PDF processing capabilities in Ghostscript where not required
• Implement sandboxing for Ghostscript processes to limit the impact of potential exploitation
• Use application whitelisting to control which applications can invoke Ghostscript
• Configure Ghostscript with the -dSAFER flag to enable sandbox mode and restrict file operations

# Run Ghostscript with SAFER mode enabled to reduce attack surface
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf input.pdf

# Verify installed Ghostscript version
gs --version

# If version is below 10.05.0, upgrade immediately
# On Debian/Ubuntu:
sudo apt update && sudo apt install ghostscript

# On RHEL/CentOS:
sudo yum update ghostscript