CVE-2025-64085

Executive Summary

CVE-2025-64085 is a NULL pointer dereference vulnerability discovered in the importDataObject() function of PDF-XChange Editor v10.7.3.401. This flaw allows an attacker to cause a Denial of Service (DoS) by providing a specially crafted input that triggers a NULL pointer dereference, leading to application crash. The vulnerability has a CVSS score of 0.0 (placeholder) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or exploit code has been released. The vendor has not yet confirmed a patch.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (PDF-XChange Editor) distributed via the vendor's website and potentially through third-party software repositories.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (placeholder – likely to be updated)
• Attack Vector: Local (requires user to open a crafted file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must open the malicious file)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High (application crash)
• Threat Level: Low (no public exploit, low EPSS)

Deep Dive & Mechanics

The vulnerability resides in the importDataObject() function within PDF-XChange Editor. This function is responsible for importing data objects from a PDF file. When a specially crafted input is provided, the function attempts to dereference a pointer that has not been properly initialized or has been set to NULL. This results in a NULL pointer dereference, causing the application to crash.

The root cause is likely insufficient validation of input data before pointer usage. An attacker can craft a malicious PDF file that, when opened, triggers this condition. The crash is immediate and does not allow for code execution, but it can be used to disrupt operations.

Vulnerable vs. Patched Code

Since no patch is available, a comparison cannot be made. However, the vulnerable code likely looks like:

void importDataObject(DataObject *obj) {
    // Vulnerable: no NULL check before dereference
    obj->type = getType(obj->data);
}

A patched version would include a NULL check:

void importDataObject(DataObject *obj) {
    if (obj == NULL) {
        // Handle error gracefully
        return;
    }
    obj->type = getType(obj->data);
}

Exploitation & Lab Setup

Red Team

1. Crafting the Malicious PDF: Use a PDF manipulation library (e.g., pdf-parser, qpdf) to create a PDF with a malformed data object that triggers the NULL pointer dereference.
2. Delivery: Send the crafted PDF via email, download link, or physical media.
3. Execution: Victim opens the PDF in PDF-XChange Editor v10.7.3.401, causing the application to crash.

Example (conceptual):

# Python script to craft a malicious PDF (simplified)
from pdfminer.pdfparser import PDFParser
from pdfminer.pdfdocument import PDFDocument

# Create a PDF with a malformed data object
# This is a placeholder – actual exploit would require reverse engineering

Blue Team

1. Detection: Monitor for crashes of PDF-XChange Editor (Event ID 1000 in Windows Application logs).
2. Prevention: Use application whitelisting to block untrusted PDF files. Enable ASLR and DEP.
3. Mitigation: Educate users not to open PDFs from untrusted sources. Use a sandboxed PDF viewer.

Indicators of Compromise (IOCs)

• File Hashes: (None available – no known malicious samples)
• Process Behavior: PDF-XChange Editor process (PDFXEdit.exe) crashes with exception code 0xC0000005 (Access Violation).
• Network: No network indicators – the crash is local.
• Registry: No persistent changes.

Detection Engineering

YARA Rule

rule CVE_2025_64085_NULL_PTR_DEREF {
    meta:
        description = "Detects PDF files likely to trigger CVE-2025-64085"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-64085"
    strings:
        $null_ptr = { 00 00 00 00 00 00 00 00 }  // Potential NULL pointer pattern
        $pdf_header = { 25 50 44 46 }  // %PDF
    condition:
        $pdf_header at 0 and #null_ptr > 5
}

Sigma Rule

title: PDF-XChange Editor Crash Due to CVE-2025-64085
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects application crash events related to PDF-XChange Editor
logsource:
    product: windows
    service: application
detection:
    selection:
        EventID: 1000
        ApplicationName: 'PDFXEdit.exe'
        ExceptionCode: '0xc0000005'
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-64085 PDF-XChange Editor DoS Attempt"; flow:to_server; content:"%PDF"; nocase; pcre:"/\/Type\s*\/\w+\s*\/\w+/"; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Vendor Patch: Await official patch from PDF-XChange. Monitor vendor website for updates.
• Workaround: Disable automatic opening of PDFs in PDF-XChange Editor. Use an alternative PDF viewer until patch is applied.
• User Education: Train users to avoid opening PDFs from untrusted sources.
• Application Control: Use software restriction policies to block PDFXEdit.exe from running in untrusted contexts.

Valters IT
Securing Digital Frontiers