CVE-2026-5937: Foxit PDF Editor DOS Vulnerability

CVE-2026-5937 Overview

CVE-2026-5937 is an unhandled exception vulnerability affecting Foxit PDF Editor and PDF Reader. The vulnerability stems from insufficient parameter verification during file processing, which leads to format errors that trigger an unhandled std::invalid_argument exception. When exploited, this exception causes the application to terminate unexpectedly, resulting in a denial of service condition.

Critical Impact

Attackers can craft malicious PDF files that crash Foxit PDF applications when opened, causing data loss and disrupting user workflows.

Affected Products

• Foxit PDF Editor
• Foxit PDF Reader

Discovery Timeline

• April 27, 2026 - CVE-2026-5937 published to NVD
• April 29, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5937

Vulnerability Analysis

This vulnerability is classified under CWE-248 (Uncaught Exception), which occurs when an application fails to properly handle exceptions that arise during execution. In the case of CVE-2026-5937, the Foxit PDF processing engine does not adequately validate input parameters before processing PDF file content. When a malformed PDF file containing unexpected or invalid data is opened, the application attempts to parse the corrupted content, resulting in a std::invalid_argument exception being thrown.

The lack of proper exception handling means this exception propagates up the call stack without being caught, ultimately causing the application to crash. This represents a denial of service vulnerability that requires local access and user interaction, as the victim must open the malicious PDF file.

Root Cause

The root cause lies in insufficient input validation within the PDF parsing routines. The application fails to verify that parameters extracted from PDF file structures conform to expected formats and ranges before processing them. When invalid data is encountered, the C++ standard library throws a std::invalid_argument exception that is not caught by the application's error handling mechanisms.

Attack Vector

The attack requires local access to the target system. An attacker would need to craft a specially malformed PDF file containing invalid parameter values designed to trigger the exception. The victim must then be convinced to open this malicious file using Foxit PDF Editor or PDF Reader. Social engineering tactics such as phishing emails with PDF attachments or hosting the malicious file on compromised websites could be used to deliver the payload.

The vulnerability mechanism involves malformed PDF content that bypasses initial validation checks but fails during deeper parsing operations. When the application encounters these malformed structures, it attempts to convert or process invalid data, triggering the std::invalid_argument exception. Without proper try-catch blocks surrounding this code path, the exception terminates the application.

Detection Methods for CVE-2026-5937

Indicators of Compromise

• Application crash logs showing std::invalid_argument exceptions in Foxit PDF Editor or Reader processes
• Windows Event Viewer entries indicating unexpected termination of FoxitPDFEditor.exe or FoxitPDFReader.exe
• Suspicious PDF files with malformed internal structures in email attachments or downloads
• Multiple PDF application crashes occurring in short succession across endpoints

Detection Strategies

• Monitor endpoint detection logs for repeated Foxit PDF application crashes
• Implement email gateway scanning to identify potentially malformed PDF attachments
• Deploy file integrity monitoring to detect suspicious PDF files in common download locations
• Configure application crash reporting to alert security teams of unusual termination patterns

Monitoring Recommendations

• Enable crash dump collection for Foxit applications to assist in forensic analysis
• Monitor for unusual patterns of PDF-related application failures across the organization
• Implement behavioral analysis to detect users receiving multiple suspicious PDF files
• Review endpoint telemetry for signs of targeted attacks using malicious documents

How to Mitigate CVE-2026-5937

Immediate Actions Required

• Update Foxit PDF Editor and PDF Reader to the latest patched versions
• Advise users to exercise caution when opening PDF files from untrusted sources
• Implement email attachment scanning and filtering for PDF files
• Consider temporarily blocking PDF attachments from external sources until patches are deployed

Patch Information

Foxit has released security updates to address this vulnerability. Administrators should consult the Foxit Security Bulletins for specific patch details and download links. It is recommended to update all affected installations as soon as possible to prevent potential denial of service attacks.

Workarounds

• Enable Protected View mode in Foxit PDF applications to provide an additional layer of isolation
• Use alternative PDF readers for documents from untrusted sources until patches are applied
• Configure endpoint protection solutions to monitor and alert on Foxit application crashes
• Implement application whitelisting to prevent execution of PDF files from untrusted locations

# Verify Foxit PDF Reader/Editor version on Windows
reg query "HKLM\SOFTWARE\Foxit Software\Foxit PDF Reader" /v Version
reg query "HKLM\SOFTWARE\Foxit Software\Foxit PDF Editor" /v Version