CVE-2021-34958
📋 TL;DR
This is a use-after-free vulnerability in Foxit PDF Editor's text annotation handling that allows remote attackers to execute arbitrary code when a user opens a malicious PDF file. Attackers can exploit this to gain control of the affected system. Users of vulnerable Foxit PDF Editor versions are affected.
💻 Affected Systems
- Foxit PDF Editor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control of the victim's machine, potentially leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Remote code execution in the context of the current user, allowing attackers to install malware, steal credentials, or establish persistence on the system.
If Mitigated
No impact if patched or if users avoid opening untrusted PDF files.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious PDF). The vulnerability was disclosed through ZDI with technical details available.
🛠️ 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 the latest version from Foxit's official website. 2. Run the installer. 3. Restart the system if prompted. 4. Verify the version is 11.1.0.52543 or higher.
🔧 Temporary Workarounds
Disable PDF file opening in Foxit Editor
windowsChange default PDF handler to a different application to prevent automatic opening in vulnerable Foxit Editor
Windows: Control Panel > Default Programs > Set Default Programs > Choose alternative PDF viewer
Application Control Restrictions
windowsUse application whitelisting to block execution of vulnerable Foxit Editor versions
🧯 If You Can't Patch
- Implement strict email filtering to block PDF attachments from untrusted sources
- Educate users to never open PDF files from unknown or untrusted sources
🔍 How to Verify
Check if Vulnerable:
Open Foxit PDF Editor, go to Help > About and check if version is below 11.1.0.52543Check Version:
Not applicable - check via GUI in Help > About menuVerify Fix Applied:
After updating, verify version is 11.1.0.52543 or higher in Help > About📡 Detection & Monitoring
Log Indicators:
- Process creation events from FoxitReader.exe with suspicious command-line arguments
- Crash logs from Foxit PDF Editor
Network Indicators:
- Unusual outbound connections from Foxit PDF Editor process
SIEM Query:
Process creation where Image contains 'FoxitReader.exe' and CommandLine contains unusual parameters or network connections