CVE-2025-69624: Nitro PDF Pro DOS Vulnerability

CVE-2025-69624 Overview

CVE-2025-69624 is a NULL pointer dereference vulnerability affecting Nitro PDF Pro for Windows version 14.41.1.4. The flaw exists in the JavaScript implementation of app.alert() within the PDF application. When app.alert() is called with more than one argument and the first argument evaluates to null, the JavaScript engine routes the call through a fallback path intended for non-string arguments. In this code path, js_ValueToString() is invoked on the null value and returns an invalid string pointer, which is subsequently passed to JS_GetStringChars() without proper validation. Dereferencing this invalid pointer results in an access violation and causes the application to crash when a user opens a specially crafted PDF document.

Critical Impact

This vulnerability can be exploited remotely by distributing malicious PDF files, leading to denial of service through application crashes when users open crafted documents.

Affected Products

• Nitro PDF Pro for Windows 14.41.1.4

Discovery Timeline

• 2026-04-13 - CVE-2025-69624 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2025-69624

Vulnerability Analysis

This vulnerability is classified under CWE-476 (NULL Pointer Dereference). The root of the issue lies in how Nitro PDF Pro's JavaScript engine handles the app.alert() function when invoked with multiple arguments where the first argument is null.

PDF documents can contain embedded JavaScript that executes when the document is opened or when specific actions occur. The app.alert() function is commonly used to display dialog boxes to users. However, when this function receives a null value as its first argument (such as when app.activeDocs returns null), the engine enters an alternative code path designed to handle non-string arguments.

The vulnerability occurs because js_ValueToString() does not properly handle the null input and returns an invalid pointer. This pointer is then used directly by JS_GetStringChars() without any validation check. When the application attempts to dereference this invalid pointer, it triggers an access violation that crashes the application.

An attacker can exploit this vulnerability by crafting a malicious PDF file containing JavaScript that triggers this specific code path. When a victim opens the PDF in Nitro PDF Pro, the application crashes, resulting in a denial of service condition.

Root Cause

The root cause is insufficient validation in the JavaScript engine's string conversion fallback path. When js_ValueToString() processes a null value, it returns an invalid string pointer rather than properly handling the error condition. The subsequent call to JS_GetStringChars() blindly accepts this invalid pointer without checking its validity, leading to an access violation when the pointer is dereferenced.

Attack Vector

The attack is network-based and requires no user interaction beyond opening a malicious PDF file. An attacker can distribute the crafted PDF through email attachments, malicious websites, or file-sharing platforms. The vulnerability requires no authentication or special privileges to exploit, making it particularly accessible to attackers.

The exploitation scenario involves embedding JavaScript code within a PDF that calls app.alert() with arguments that cause the first parameter to evaluate to null, such as app.alert(app.activeDocs, true) when app.activeDocs is null.

Detection Methods for CVE-2025-69624

Indicators of Compromise

• PDF files containing JavaScript with calls to app.alert() using multiple arguments where the first argument references potentially null properties
• Application crash logs from Nitro PDF Pro showing access violations in the JavaScript engine components
• Repeated crashes when attempting to open specific PDF files

Detection Strategies

• Monitor for Nitro PDF Pro application crashes with access violation exceptions, particularly those occurring during PDF document opening
• Implement PDF scanning solutions that analyze embedded JavaScript for suspicious app.alert() patterns with null-evaluating arguments
• Deploy endpoint detection rules to identify crash patterns associated with this vulnerability

Monitoring Recommendations

• Enable crash reporting and monitoring for Nitro PDF Pro installations across the enterprise
• Implement email gateway scanning for PDF attachments containing potentially malicious JavaScript
• Monitor file system activity for PDF files being opened followed by application crashes

How to Mitigate CVE-2025-69624

Immediate Actions Required

• Restrict opening of PDF files from untrusted sources until a patch is available
• Consider disabling JavaScript execution in Nitro PDF Pro if the feature is not essential for business operations
• Implement network-level filtering to block known malicious PDF files
• Educate users about the risks of opening PDF attachments from unknown senders

Patch Information

Organizations should monitor the Nitro Security Overview page for updates regarding security patches for this vulnerability. As of the last NVD update, specific patch information has not been published. Contact Nitro support for the latest security guidance and available fixes.

Workarounds

• Disable JavaScript execution in Nitro PDF Pro through the application preferences to prevent exploitation of this vulnerability
• Use alternative PDF readers for viewing untrusted documents until a patch is available
• Implement document sanitization solutions that strip JavaScript from incoming PDF files before delivery to end users
• Deploy application whitelisting to prevent execution of modified or potentially malicious PDF files