CVE-2021-34956
📋 TL;DR
This is a use-after-free vulnerability in Foxit PDF Editor's underline annotation handling that allows remote attackers to execute arbitrary code. Users who open malicious PDF files or visit malicious web pages with Foxit PDF Editor are affected. The vulnerability exists due to improper validation of annotation objects before operations.
💻 Affected Systems
- Foxit PDF Editor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining the same privileges as the current user, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
Local privilege escalation or arbitrary code execution within the context of the Foxit PDF Editor process, potentially leading to malware installation.
If Mitigated
Limited impact due to sandboxing or application hardening, potentially only application crash or denial of service.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious PDF). The vulnerability was discovered by Zero Day Initiative (ZDI-CAN-14357).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.1.0.52543 and later
Vendor Advisory: https://www.foxit.com/support/security-bulletins.html
Restart Required: Yes
Instructions:
1. Download latest version from Foxit website. 2. Run installer. 3. Restart system. 4. Verify version is 11.1.0.52543 or higher.
🔧 Temporary Workarounds
Disable PDF opening in Foxit Editor
windowsChange default PDF handler to alternative PDF reader
Control Panel > Default Programs > Set Default Programs > Select alternative PDF reader
Application sandboxing
windowsRun Foxit PDF Editor in restricted environment
🧯 If You Can't Patch
- Use alternative PDF software for opening untrusted PDFs
- Implement application whitelisting to prevent unauthorized execution
🔍 How to Verify
Check if Vulnerable:
Check Foxit PDF Editor version in Help > About. If version is below 11.1.0.52543, system is vulnerable.Check Version:
In Foxit PDF Editor: Help > AboutVerify Fix Applied:
Verify version is 11.1.0.52543 or higher in Help > About. Test opening known safe PDFs to ensure functionality.📡 Detection & Monitoring
Log Indicators:
- Application crashes of Foxit PDF Editor
- Unusual process creation from Foxit PDF Editor
Network Indicators:
- Downloads of PDF files from suspicious sources
- Outbound connections from Foxit process to unknown IPs
SIEM Query:
Process:foxit* AND (EventID:1000 OR ParentImage:*foxit*)