CVE-2025-66769: Nitro PDF Pro DoS Vulnerability

CVE-2025-66769 Overview

A NULL pointer dereference vulnerability exists in Nitro PDF Pro for Windows version 14.41.1.4 that allows attackers to cause a Denial of Service (DoS) condition. The vulnerability is triggered when the application processes a specially crafted XFA (XML Forms Architecture) packet embedded within a PDF document. When exploited, the application crashes due to dereferencing an invalid memory address, resulting in service disruption for affected users.

Critical Impact

This vulnerability enables remote attackers to crash Nitro PDF Pro without authentication, potentially disrupting business workflows that depend on PDF processing capabilities.

Affected Products

• Nitro PDF Pro for Windows v14.41.1.4

Discovery Timeline

• 2026-04-13 - CVE-2025-66769 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2025-66769

Vulnerability Analysis

This vulnerability is classified as CWE-476 (NULL Pointer Dereference), a memory corruption issue that occurs when the application attempts to use a pointer that references a NULL memory address. In the context of Nitro PDF Pro, the flaw manifests during the parsing of XFA packets within PDF documents. XFA is a deprecated but still supported XML-based architecture used for creating dynamic forms within PDF files.

When a maliciously crafted XFA packet is processed by the vulnerable version of Nitro PDF Pro, the application fails to properly validate pointer references before dereferencing them. This results in the application attempting to read from or write to memory address 0x0, which is a protected memory region on modern operating systems, causing an immediate application crash.

The network-based attack vector indicates that exploitation can occur when a user opens a malicious PDF document received via email, downloaded from a compromised website, or accessed through a file share. No authentication or user interaction beyond opening the crafted document is required for exploitation.

Root Cause

The root cause of this vulnerability stems from inadequate input validation in the XFA packet parser. When processing certain malformed XFA elements, the parser fails to verify that required object pointers are properly initialized before accessing their members or methods. This missing null-check allows an attacker to craft an XFA structure that triggers the vulnerable code path with uninitialized or explicitly nullified pointer values.

Attack Vector

The attack is delivered through a network-accessible vector, requiring the victim to open a malicious PDF document containing the crafted XFA payload. The attacker constructs a PDF file with an embedded XFA form containing malformed XML structures designed to trigger the null pointer dereference during parsing.

The attack sequence involves:

1. Attacker creates a malicious PDF with a crafted XFA packet
2. Victim receives the PDF via email, download, or file share
3. Victim opens the PDF in Nitro PDF Pro v14.41.1.4
4. XFA parser processes the malformed packet
5. Application crashes due to NULL pointer dereference

For technical details on the vulnerability mechanism, refer to the Jeroscope Advisory JERO-2025-015.

Detection Methods for CVE-2025-66769

Indicators of Compromise

• Unexpected crashes or termination of NitroPDF.exe process when opening PDF documents
• Windows Event Log entries showing application faults in Nitro PDF Pro with exception code indicating access violation (0xC0000005)
• Repeated application crashes with crash dumps pointing to XFA parsing modules
• PDF files with unusually structured or malformed XFA streams in document analysis

Detection Strategies

• Deploy endpoint detection rules to monitor for repeated Nitro PDF Pro application crashes
• Implement email gateway scanning to detect and quarantine PDF attachments with suspicious XFA structures
• Configure SentinelOne behavioral AI to detect anomalous application termination patterns
• Use file analysis tools to inspect incoming PDFs for malformed XFA content before user access

Monitoring Recommendations

• Enable application crash monitoring for Nitro PDF Pro installations across the enterprise
• Configure Windows Error Reporting to capture crash dumps for forensic analysis
• Monitor file servers and email systems for PDF files with anomalous XFA packet structures
• Implement network traffic analysis to identify potential delivery of malicious PDF documents

How to Mitigate CVE-2025-66769

Immediate Actions Required

• Upgrade Nitro PDF Pro to the latest version available from GoNitro
• Restrict processing of PDF documents with XFA content until patching is complete
• Implement enhanced email filtering to scan and quarantine suspicious PDF attachments
• Consider temporary use of alternative PDF readers for high-risk document processing

Patch Information

Users should check the GoNitro Security Page for the latest security updates and patches addressing this vulnerability. Organizations should prioritize updating all instances of Nitro PDF Pro v14.41.1.4 to the newest available version.

Additional technical information is available in the Jeroscope Advisory JERO-2025-015.

Workarounds

• Disable XFA form processing in Nitro PDF Pro if configuration options allow
• Use application sandboxing or virtual environments when opening untrusted PDF documents
• Implement organizational policies to scan all incoming PDF files before user access
• Consider blocking or quarantining PDF files containing XFA content at email gateways and web proxies

# Configuration example - Implement controlled folder access to protect against crashes
# Enable Windows Defender Controlled Folder Access for additional protection
Set-MpPreference -EnableControlledFolderAccess Enabled

# Add Nitro PDF Pro to monitored applications
Add-MpPreference -ControlledFolderAccessAllowedApplications "C:\Program Files\Nitro\Pro\14\NitroPDF.exe"