CVE-2021-21822
📋 TL;DR
A use-after-free vulnerability in Foxit PDF Reader's JavaScript engine allows arbitrary code execution when users open malicious PDF files. This affects Foxit PDF Reader version 10.1.3.37598 users, particularly when the browser plugin extension is enabled. Attackers can exploit this by tricking users into opening specially crafted PDF documents.
💻 Affected Systems
- Foxit PDF Reader
📦 What is this software?
Foxit Reader by Foxitsoftware
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining the same privileges as the user, potentially leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malware installation leading to credential theft, data exfiltration, or system disruption for individual users.
If Mitigated
Limited impact with proper application sandboxing and user privilege restrictions, potentially only crashing the PDF reader application.
🎯 Exploit Status
Exploitation requires user interaction but has been publicly documented in vulnerability reports.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.1.4 or later
Vendor Advisory: https://www.foxit.com/support/security-bulletins.html
Restart Required: Yes
Instructions:
1. Open Foxit PDF Reader. 2. Go to Help > Check for Updates. 3. Follow prompts to install latest version. 4. Restart computer after installation.
🔧 Temporary Workarounds
Disable JavaScript in Foxit Reader
allPrevents JavaScript execution in PDF files, mitigating the vulnerability.
Open Foxit Reader > File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Disable Browser Plugin
allPrevents exploitation via web browsers.
Open Foxit Reader > File > Preferences > General > Uncheck 'Enable PDF viewing in web browsers'
🧯 If You Can't Patch
- Restrict PDF file opening to trusted sources only
- Run Foxit Reader with limited user privileges
🔍 How to Verify
Check if Vulnerable:
Check Foxit Reader version: Open Foxit > Help > About Foxit Reader. If version is 10.1.3.37598 or earlier, system is vulnerable.Check Version:
On Windows: wmic product where name="Foxit Reader" get versionVerify Fix Applied:
Verify version is 10.1.4 or later in Help > About Foxit Reader.📡 Detection & Monitoring
Log Indicators:
- Multiple Foxit Reader crashes
- Unusual process spawning from Foxit Reader
Network Indicators:
- Unexpected outbound connections from Foxit Reader process
SIEM Query:
process_name:"FoxitReader.exe" AND (event_id:1000 OR event_id:1001) | where version contains "10.1.3"