CVE-2025-6654: PDF-XChange Editor PRC File RCE Flaw

CVE-2025-6654 Overview

CVE-2025-6654 is an out-of-bounds write vulnerability in PDF-XChange Editor that allows remote attackers to execute arbitrary code on affected installations. This vulnerability exists within the parsing of PRC (Product Representation Compact) files, a 3D data format commonly embedded in PDF documents. User interaction is required to exploit this vulnerability—the target must either visit a malicious webpage or open a maliciously crafted file.

The specific flaw stems from the lack of proper validation of user-supplied data during PRC file parsing, which can result in a write operation past the end of an allocated buffer. An attacker who successfully exploits this vulnerability can execute arbitrary code in the context of the current process, potentially leading to complete system compromise.

Critical Impact

Successful exploitation allows arbitrary code execution in the context of the current user. If the user has administrative privileges, an attacker could take full control of the affected system, install malware, exfiltrate sensitive data, or use it as a pivot point for lateral movement within a network.

Affected Products

• PDF-XChange Editor version 10.5.2.395
• PDF-XChange PDF-Tools version 10.5.2.395
• Earlier versions may also be affected

Discovery Timeline

• 2025-06-25 - CVE-2025-6654 published to NVD
• 2025-07-01 - Last updated in NVD database

Technical Details for CVE-2025-6654

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption flaw that occurs when a program writes data past the boundaries of an allocated memory buffer. In the context of PDF-XChange Editor, the vulnerability manifests during the parsing of PRC files, which are 3D CAD data containers that can be embedded within PDF documents.

The root cause lies in insufficient bounds checking when processing user-controlled data within PRC file structures. When the parser encounters a malformed PRC file with specially crafted size or length fields, it fails to validate that the data being written fits within the allocated buffer space. This oversight allows an attacker to corrupt adjacent memory regions.

The exploitation requires local attack vector with user interaction—meaning the victim must be tricked into opening a malicious document or visiting a compromised webpage. Despite this requirement, the potential impact is severe as successful exploitation results in arbitrary code execution with the privileges of the current user.

Root Cause

The vulnerability originates from improper input validation within the PRC file parsing routines of PDF-XChange Editor. When processing PRC file structures, the application allocates memory buffers based on size values specified within the file format. However, the parser fails to adequately verify that subsequent data operations stay within the bounds of these allocated buffers.

Specifically, when the parser reads and processes element data from the PRC stream, it trusts user-controlled length fields without sufficient validation. This allows a malformed file to specify data lengths that exceed buffer boundaries, causing the application to write past the end of allocated memory.

Attack Vector

An attacker can exploit this vulnerability through multiple vectors:

1. Malicious Document Delivery: Crafting a PDF document containing an embedded malicious PRC file and distributing it via email, file sharing, or download links
2. Drive-by Download: Hosting a malicious PRC file or PDF on a compromised or attacker-controlled website
3. Watering Hole Attacks: Targeting specific organizations by compromising websites frequently visited by their employees

The attack requires social engineering to convince the target to open the malicious file. Once opened in a vulnerable version of PDF-XChange Editor, the malformed PRC data triggers the out-of-bounds write condition. The attacker can carefully craft the overflow data to overwrite critical memory structures such as function pointers or return addresses, ultimately redirecting execution to attacker-controlled shellcode.

The vulnerability was tracked by the Zero Day Initiative as ZDI-CAN-26729 and published as ZDI-25-439.

Detection Methods for CVE-2025-6654

Indicators of Compromise

• Unexpected crashes or abnormal termination of PDF-XChange Editor processes
• PDF documents containing embedded PRC files from untrusted sources
• Suspicious child processes spawned from PDF-XChange Editor (e.g., cmd.exe, powershell.exe)
• Memory access violations or exception handling errors in application logs

Detection Strategies

• Monitor for PDF-XChange Editor process creating unexpected child processes, particularly command shells or scripting engines
• Implement file inspection at email gateways and web proxies to detect PDF files containing PRC streams with anomalous size values
• Deploy endpoint detection rules to identify memory corruption exploitation attempts in document processing applications
• Analyze crash dumps from PDF-XChange Editor for signs of heap corruption or controlled memory overwrites

Monitoring Recommendations

• Enable detailed application logging and crash reporting for PDF-XChange Editor installations
• Implement network monitoring for unusual outbound connections following document opening events
• Configure endpoint telemetry to capture process creation chains originating from document applications
• Review security event logs for DEP (Data Execution Prevention) or ASLR violations in PDF-XChange processes

How to Mitigate CVE-2025-6654

Immediate Actions Required

• Update PDF-XChange Editor and PDF-Tools to the latest patched version available from the vendor
• Implement user awareness training to warn against opening PDF documents from untrusted or unexpected sources
• Consider temporarily restricting the processing of PDF files containing 3D/PRC content in high-risk environments
• Deploy application whitelisting or sandboxing to limit the impact of successful exploitation

Patch Information

PDF-XChange has released security updates addressing this vulnerability. Organizations should consult the PDF-XChange Security Bulletins for the latest patch information and update instructions. Ensure all instances of PDF-XChange Editor version 10.5.2.395 and PDF-Tools version 10.5.2.395 are updated to the remediated versions.

For detailed technical information about this vulnerability, refer to the Zero Day Initiative Advisory ZDI-25-439.

Workarounds

• Configure PDF-XChange Editor to disable 3D/PRC content rendering if the feature is not business-critical
• Use Protected View or sandbox mode when opening documents from untrusted sources
• Implement email attachment filtering to quarantine or strip PDF documents containing PRC streams
• Consider using alternative PDF readers in high-security environments until patches can be applied

# Configuration example - Restrict execution from temporary directories commonly used during exploitation
# Windows AppLocker policy to block execution from common exploitation paths
# Apply via Group Policy or local security policy

# PowerShell command to check installed PDF-XChange version
Get-ItemProperty "HKLM:\SOFTWARE\Tracker Software\PDF-XChange Editor" -Name "Version" -ErrorAction SilentlyContinue

# Verify all PDF-XChange installations are updated
Get-WmiObject -Class Win32_Product | Where-Object { $_.Name -like "*PDF-XChange*" } | Select-Object Name, Version