CVE-2021-34954
📋 TL;DR
This is a use-after-free vulnerability in Foxit PDF Editor's handling of StrikeOut annotations that allows remote code execution. Attackers can exploit it by tricking users into opening malicious PDF files, potentially compromising affected systems. Users of vulnerable Foxit PDF Editor versions are at risk.
💻 Affected Systems
- Foxit PDF Editor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining the same privileges as the current user, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
Malicious code execution in user context leading to credential theft, data exfiltration, or malware installation.
If Mitigated
Limited impact with proper application sandboxing and user privilege restrictions, potentially only application crash.
🎯 Exploit Status
Requires user interaction to open malicious PDF. ZDI published technical details but no public exploit code.
🛠️ 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 handling in Foxit
windowsSet Windows default PDF handler to alternative application
Control Panel > Default Programs > Set Default Programs > Select alternative PDF reader
Application Control Policy
windowsBlock execution of vulnerable Foxit versions via AppLocker or similar
New-AppLockerPolicy -RuleType Publisher,Path -User Everyone -Action Deny
🧯 If You Can't Patch
- Implement application sandboxing to limit impact of potential exploitation
- Restrict user privileges to prevent system-wide compromise if exploited
🔍 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:
wmic product where name="Foxit PDF Editor" get versionVerify Fix Applied:
Verify version is 11.1.0.52543 or higher in Help > About and test opening known safe PDFs with StrikeOut annotations.📡 Detection & Monitoring
Log Indicators:
- Application crashes with exception codes related to memory access violations
- Unusual child processes spawned from FoxitPDFEditor.exe
Network Indicators:
- Unexpected outbound connections from Foxit process post-PDF opening
- DNS requests to suspicious domains after PDF processing
SIEM Query:
process_name="FoxitPDFEditor.exe" AND (event_id=1000 OR child_process_creation=true)