CVE-2025-27830: Artifex Ghostscript Buffer Overflow Flaw

CVE-2025-27830 Overview

CVE-2025-27830 is a buffer overflow vulnerability discovered in Artifex Ghostscript before version 10.05.0. The vulnerability occurs during the serialization of DollarBlend in a font, specifically affecting the base/write_t1.c and psi/zfapi.c source files. This memory corruption flaw can potentially allow attackers to execute arbitrary code or cause a denial of service condition when processing maliciously crafted font data.

Critical Impact

A buffer overflow in Ghostscript's font serialization process could allow attackers to achieve code execution or crash the application through specially crafted PostScript or PDF documents containing malicious font data.

Affected Products

• Artifex Ghostscript versions prior to 10.05.0

Discovery Timeline

• 2025-03-25 - CVE-2025-27830 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-27830

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 resides in Ghostscript's font handling subsystem, specifically within the code responsible for serializing DollarBlend data structures in Type 1 fonts.

Ghostscript is a widely-used interpreter for PostScript and PDF files, making it a critical component in many document processing pipelines, print servers, and image conversion utilities. The vulnerability's local attack vector requires user interaction, typically through opening a malicious document, but the potential impact includes full compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of CVE-2025-27830 lies in insufficient bounds checking during the serialization of DollarBlend font data. The affected code in base/write_t1.c and psi/zfapi.c fails to properly validate the size of input data before copying it into fixed-size buffers. When processing specially crafted font structures, this oversight allows data to overflow beyond the allocated buffer boundaries, potentially corrupting adjacent memory regions.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to convince a user to open a maliciously crafted file. Attack scenarios include:

1. Document-based attacks: An attacker crafts a PostScript or PDF file containing a malformed DollarBlend font structure designed to trigger the buffer overflow when Ghostscript processes the document.

2. Print server exploitation: In environments where Ghostscript processes documents automatically (such as print servers or document conversion services), an attacker could submit malicious documents to trigger the vulnerability without direct user interaction.

3. Image conversion pipelines: Applications using Ghostscript for image conversion (such as ImageMagick with Ghostscript delegates) may be vulnerable when processing untrusted input files.

The vulnerability is triggered during font serialization operations when the DollarBlend data contains oversized or malformed elements that exceed the expected buffer capacity.

Detection Methods for CVE-2025-27830

Indicators of Compromise

• Unexpected crashes or segmentation faults in Ghostscript processes (gs, ghostscript) when processing documents
• Abnormal memory consumption patterns during PDF or PostScript document processing
• Core dumps or crash reports referencing write_t1.c or zfapi.c in stack traces
• Suspicious PostScript or PDF files with unusual font structures being processed by print spoolers or document converters

Detection Strategies

• Monitor Ghostscript processes for abnormal behavior including crashes, high memory usage, or unexpected child process spawning
• Implement file integrity monitoring on systems running Ghostscript to detect post-exploitation modifications
• Deploy endpoint detection solutions capable of identifying buffer overflow exploitation attempts
• Review application logs for errors related to font processing or serialization failures in Ghostscript

Monitoring Recommendations

• Enable crash reporting and logging for all Ghostscript instances in production environments
• Configure centralized logging to capture Ghostscript process errors and correlate them across systems
• Implement alerting for repeated Ghostscript crashes which may indicate exploitation attempts
• Monitor network traffic for suspicious document transfers to systems running vulnerable Ghostscript versions

How to Mitigate CVE-2025-27830

Immediate Actions Required

• Upgrade Artifex Ghostscript to version 10.05.0 or later immediately
• Audit systems to identify all instances of Ghostscript installations, including those bundled with other software
• Restrict processing of untrusted PostScript and PDF documents until patching is complete
• Consider implementing sandboxing for Ghostscript processes to limit potential exploitation impact

Patch Information

Artifex has addressed this vulnerability in Ghostscript version 10.05.0. The fix includes proper bounds checking during DollarBlend font serialization to prevent buffer overflow conditions. Detailed information about the fix is available in the Ghostscript Bug Report #708241.

Additionally, Debian has released security updates addressing this vulnerability as documented in the Debian LTS Announcement. Users of Debian-based distributions should apply available security updates through their package manager.

Workarounds

• Disable processing of Type 1 fonts if your workflow permits by using Ghostscript's -dDONTUSEFONTS or font-related restriction options
• Implement input validation to reject documents with suspicious font structures before processing with Ghostscript
• Run Ghostscript in sandboxed environments or containers with restricted privileges to limit exploitation impact
• Use the -dSAFER flag when invoking Ghostscript to enable safer execution mode (note: this may not fully mitigate this specific vulnerability)

# Example: Running Ghostscript with restricted permissions
# Apply SAFER mode and restrict file operations
gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sOutputFile=output.pdf input.ps

# Verify installed Ghostscript version
gs --version

# On Debian/Ubuntu, update to patched version
sudo apt update && sudo apt upgrade ghostscript