CVE-2021-34851
📋 TL;DR
This vulnerability in Foxit PDF Reader allows remote attackers to execute arbitrary code by tricking users into opening malicious PDF files. The flaw exists in how Annotation objects are handled without proper validation, leading to use-after-free conditions. Users of affected Foxit PDF Reader versions are at risk.
💻 Affected Systems
- Foxit PDF Reader
📦 What is this software?
Pdf Editor by Foxitsoftware
Pdf Editor by Foxitsoftware
⚠️ 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
Malware installation or data exfiltration through spear-phishing campaigns using weaponized PDF documents.
If Mitigated
Limited impact with proper endpoint protection, application sandboxing, and user awareness training preventing successful exploitation.
🎯 Exploit Status
Exploitation requires user interaction but is straightforward once malicious PDF is opened. ZDI-CAN-14016 identifier suggests detailed research exists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.0.1 or later
Vendor Advisory: https://www.foxit.com/support/security-bulletins.html
Restart Required: Yes
Instructions:
1. Download latest Foxit PDF Reader from official website
2. Uninstall current version
3. Install updated version
4. Restart system
🔧 Temporary Workarounds
Disable JavaScript in Foxit Reader
windowsPrevents JavaScript-based exploitation vectors
Open Foxit Reader > File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use Protected View
windowsOpen PDFs in sandboxed mode
Open Foxit Reader > File > Preferences > Trust Manager > Check 'Enable Safe Reading Mode'
🧯 If You Can't Patch
- Use alternative PDF reader software temporarily
- Block PDF files from untrusted sources at email/web gateway
🔍 How to Verify
Check if Vulnerable:
Check Foxit Reader version in Help > About. If version is 11.0.0.49893 or earlier, system is vulnerable.Check Version:
wmic product where name="Foxit Reader" get versionVerify Fix Applied:
Verify version is 11.0.1 or later in Help > About.📡 Detection & Monitoring
Log Indicators:
- Foxit Reader crash logs with exception codes
- Unexpected child processes spawned from Foxit Reader
Network Indicators:
- Outbound connections from Foxit Reader to suspicious IPs
- DNS requests for known malicious domains
SIEM Query:
process_name:"FoxitReader.exe" AND (event_id:1000 OR parent_process_name:"FoxitReader.exe")