CVE-2025-27833: Artifex Ghostscript Buffer Overflow Flaw

CVE-2025-27833 Overview

CVE-2025-27833 is a buffer overflow vulnerability discovered in Artifex Ghostscript before version 10.05.0. The vulnerability occurs in the pdf/pdf_fmap.c file when processing TrueType Font (TTF) names that exceed expected length boundaries. This memory corruption flaw can be triggered when Ghostscript processes specially crafted documents containing malicious TTF font references.

Critical Impact

Successful exploitation of this buffer overflow vulnerability could allow an attacker to execute arbitrary code with the privileges of the user running Ghostscript, potentially leading to full system compromise when processing malicious PDF or PostScript files.

Affected Products

• Artifex Ghostscript versions prior to 10.05.0
• Applications and services that utilize Ghostscript for PDF/PostScript processing
• Document conversion pipelines and print spoolers integrating vulnerable Ghostscript versions

Discovery Timeline

• 2025-03-25 - CVE-2025-27833 published to NVD
• 2025-04-01 - Last updated in NVD database

Technical Details for CVE-2025-27833

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 exists in the font mapping functionality within Ghostscript's PDF processing subsystem, specifically in the pdf/pdf_fmap.c source file.

When Ghostscript parses PDF documents containing embedded or referenced TrueType fonts, it processes font name strings as part of the font mapping routine. The vulnerable code path fails to properly validate the length of TTF font names before copying them into fixed-size buffers. An attacker can craft a malicious document with an excessively long font name that overflows the destination buffer, corrupting adjacent memory regions.

The local attack vector requires user interaction, meaning the victim must open or process a malicious file. However, this is a common scenario in environments where Ghostscript is used for automated document processing, print services, or PDF conversion workflows.

Root Cause

The root cause of CVE-2025-27833 is insufficient bounds checking in the font name handling code within pdf/pdf_fmap.c. When a TTF font name is encountered during PDF parsing, the code copies the name string into a buffer without first verifying that the source string length does not exceed the allocated buffer size. This classic buffer overflow pattern allows memory corruption when processing fonts with names exceeding the expected maximum length.

Attack Vector

The attack vector for this vulnerability is local, requiring the attacker to deliver a malicious file to the target system. Exploitation scenarios include:

1. Malicious Document Delivery: An attacker sends a crafted PDF document via email or file sharing that contains an embedded TTF font with an overly long name
2. Automated Processing Pipelines: Systems that automatically process incoming documents (print servers, document converters) are particularly at risk
3. Web-Based Conversion Services: Online services using Ghostscript for PDF processing could be exploited through malicious file uploads

The vulnerability manifests when Ghostscript processes a PDF document containing a TrueType font reference with an excessively long name. The font name string overflows the fixed-size buffer in pdf/pdf_fmap.c, potentially allowing an attacker to overwrite adjacent memory, corrupt program state, and achieve code execution. For detailed technical analysis, refer to Ghostscript Bug Report #708259.

Detection Methods for CVE-2025-27833

Indicators of Compromise

• Ghostscript process crashes or unexpected terminations when processing PDF files
• Unusual memory access violations or segmentation faults in Ghostscript processes
• PDF files containing fonts with abnormally long name strings (exceeding typical 256 character boundaries)
• Suspicious PDF documents with embedded or referenced TTF fonts from untrusted sources

Detection Strategies

• Monitor Ghostscript processes for abnormal crash patterns or memory corruption indicators
• Implement file inspection rules to detect PDF documents with excessively long font name entries
• Deploy endpoint detection rules that identify exploitation attempts targeting Ghostscript
• Enable crash dump analysis for Ghostscript-related processes to identify buffer overflow exploitation

Monitoring Recommendations

• Log all Ghostscript process executions and their input file sources
• Monitor for unusual process behavior including unexpected child process spawning from Ghostscript
• Implement network monitoring for systems that provide Ghostscript-based document conversion services
• Track file uploads to document processing services and flag suspicious PDF structures

How to Mitigate CVE-2025-27833

Immediate Actions Required

• Upgrade Artifex Ghostscript to version 10.05.0 or later immediately
• Restrict Ghostscript processing to trusted documents only until patching is complete
• Implement sandbox isolation for Ghostscript processes handling untrusted files
• Review and audit document processing workflows that utilize Ghostscript

Patch Information

Artifex has addressed this vulnerability in Ghostscript version 10.05.0. Organizations should prioritize upgrading to this version or later to remediate the buffer overflow vulnerability. Detailed patch information and discussion can be found in the Ghostscript Bug Report #708259.

Workarounds

• Run Ghostscript in a sandboxed environment with restricted permissions to limit exploitation impact
• Disable or restrict TTF font processing if not required for your use case
• Implement input validation to reject PDF documents with suspicious font structures before processing
• Use -dSAFER flag when invoking Ghostscript to enable safer mode restrictions

# Configuration example - Running Ghostscript with safer mode enabled
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf input.pdf

# Sandboxing Ghostscript execution with firejail
firejail --private --net=none gs -dSAFER -dBATCH input.pdf