CVE-2021-34974
📋 TL;DR
This is a use-after-free vulnerability in Foxit PDF Reader's annotation handling that allows remote attackers to execute arbitrary code when a user opens a malicious PDF file. It affects Foxit PDF Reader users who open untrusted PDF documents. The vulnerability exists due to improper validation of annotation objects before operations.
💻 Affected Systems
- Foxit PDF Reader
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining the same privileges as the PDF Reader process, potentially leading to malware installation, data theft, or lateral movement.
Likely Case
Local code execution with user privileges, allowing attackers to steal files, install keyloggers, or establish persistence on the compromised system.
If Mitigated
Limited impact if PDF Reader runs with restricted privileges or in sandboxed environments, potentially only causing application crashes.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious PDF) but is relatively straightforward once the malicious file is executed. The vulnerability was discovered by Zero Day Initiative.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.0.1 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 update to version 11.0.1 or later
4. Restart the application
🔧 Temporary Workarounds
Disable JavaScript in Foxit Reader
windowsPrevents JavaScript-based exploitation vectors that might be used to trigger the vulnerability
Open Foxit Reader > File > Preferences > JavaScript > Uncheck 'Enable JavaScript'
Use alternative PDF viewer
allTemporarily use a different PDF reader that is not affected by this vulnerability
🧯 If You Can't Patch
- Restrict PDF Reader to run with minimal user privileges using application control policies
- Block PDF files from untrusted sources at network perimeter and email gateways
🔍 How to Verify
Check if Vulnerable:
Check Foxit Reader version: Open Foxit Reader > Help > About Foxit Reader. If version is below 11.0.1, system is vulnerable.Check Version:
wmic product where name="Foxit Reader" get versionVerify Fix Applied:
Verify version is 11.0.1 or higher in Help > About Foxit Reader📡 Detection & Monitoring
Log Indicators:
- Application crashes of Foxit Reader with memory access violations
- Unusual process creation from Foxit Reader process
Network Indicators:
- Downloads of PDF files from suspicious sources followed by Foxit Reader execution
SIEM Query:
Process Creation where (Image contains "FoxitReader.exe") AND (CommandLine contains ".pdf")