CVE-2021-34847
📋 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, enabling code execution in the current process context. 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 via remote code execution, potentially leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Malware installation or data exfiltration when users open malicious PDFs from phishing emails or compromised websites.
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 advisory suggests weaponization is likely.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.0.0.49894 and 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 application after update
🔧 Temporary Workarounds
Disable JavaScript in Foxit Reader
allPrevents JavaScript-based exploitation vectors
File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use Protected View
windowsOpens PDFs in sandboxed mode
File > Preferences > Trust Manager > Check 'Enable Safe Reading Mode'
🧯 If You Can't Patch
- Use alternative PDF readers that are not vulnerable
- Block PDF files from untrusted sources at network perimeter
🔍 How to Verify
Check if Vulnerable:
Check Foxit Reader version: Help > About Foxit Reader. If version is 11.0.0.49893 or earlier, system is vulnerable.Check Version:
On Windows: wmic product where name="Foxit Reader" get versionVerify Fix Applied:
Verify version is 11.0.0.49894 or later in Help > About Foxit Reader.📡 Detection & Monitoring
Log Indicators:
- Foxit Reader crash logs with memory access violations
- Unexpected child processes spawned from Foxit Reader
Network Indicators:
- Outbound connections from Foxit Reader to unknown IPs
- DNS requests for suspicious domains after PDF opening
SIEM Query:
process_name:"FoxitReader.exe" AND (event_id:1000 OR parent_process_name:"FoxitReader.exe")